This is my experience too.
I work in schools and I feel a surge of pain every time I am asked to buy a license for something like SQL Server or Windows Server for some job that could more easily be done some other way (not just monetary, but technically too). Our fax server is a Linux machine running OS software for the task. Our IM server is a Linux machine running OS software for the task. Our web filter is a Linux machine running OS software for the task. Our firewall, our file storage server, our intranet, our website, some of our databases, our network scanning, our print management, our offline backups, etc. If I bought a Windows server for each task (and I would need 2-3x as many Windows servers as Linux servers at best anyway - all that runs off ONE machine that's doing a lot more besides) I'd spend thousands and thousands just on licences. When you *need* high-powered SQL, then it's worth paying for it. When you don't (e.g. your own website, intranet, other menial tasks etc.), then a MySQL instance is more than enough (and some would say even too much!).
The proprietary access-control software that I installed in work uses the FireBird SQL server - it's like SQLite and designed for use in programs running on all OS. Everything it does is queriable via SQL using the appropriate standardised tools but it saves in a simple small backup-able file on your normal filesystem (and thus you can easily backup, restore, have multiple installs, etc.) and is ideal for small database installs on Windows (or even Linux - it has Linux tools and the above Linux server queries the access control system every 30 seconds or so to make a primitive In/Out board). Firebird takes literally seconds to install from scratch. We really *don't* need an installation of SQL Server (or even Express) like the boiler-control software I have uses to store historical boiler temperatures that the software itself won't even let you query anyway but won't install without (and took 2 hours to reinstall after a server crash the other day).
Sometimes, you know, a simpler, smaller tool is better for the job. You can keep all your fancy grass-collecting drive-on lawnmowers when you only have 6ft of lawn to cut anyway because it's wasteful and unnecessary. If you told people that they would have to pay a licence for the shelves you fit in their house, they'd pop down to B&Q and learn how to fit one themselves. But when it comes to software, they will happily spend hundreds on Windows, hundreds more on Office, THOUSANDS on SQL Server and Exchange (and people to manage it), more on things like WinZip etc. and be no better off than if they'd replaced most of those components with OS software.
That doesn't mean there aren't places that benefit from that software but the truth is that 90% of small businesses wouldn't.
Linux as an OS replacement for Windows is a big step, it has to be said, but it's still perfectly viable for servers where you don't CARE because the only people to sit down in front of it and start fiddling with your database internals are going to be technical anyway (and probably don't care what OS it's on). But silly, everyday things don't all need stonking great CAL's for hugely over-complex programs all the time. Seriously, do I *really* need Windows and an SQL Server install to see that my boiler is running a little hot and lower the threshold? No. Do I need it to store the database of people and cards that can access the site? No. Do I need it to run a Mediawiki intranet? No. Do I need it to run most small-business databases at all? No. But people get told what to buy by other businesses and apply the advice literally without thinking. A small office does NOT need an Exchange server (where just a plain email server would do with some basic calendaring software), or a huge Windows Server to store files (when a small NAS box or Linux Samba share would do), or SQL Server for a database accessed by a handful of people (when a small MySQL or even flat-file databases would do).
And you have to think of ongoing costs. If your system rely on SQL Server, you need someone who can manage it. You also need to keep it running all the time. And you need to upgrade it when the software that "needs" it requires an upgrade. And you might need to install redundant backup servers that can take over that task from others, etc. The costs soon spiral ridiculously for something that wasn't necessary.
Disclaimer: I spent my entire adult career moving schools from RM to plain Microsoft systems (because, believe it or not, that was a huge step in the right direction) and have spent the last few years slowly migrating a private school to Linux where appropriate. I'd saved them my annual salary in licensing, extra hardware, etc. within the first few months with ZERO compromise of expected functionality, availability, reliability, backup, etc.
It's not for everything (anyone that tells you that Linux can do it all should be viewed in the same light as someone saying that a screwdriver can be made to do every job for every level of the service sector) but it can surely replace a lot of nonsensical, wasteful uses of technology.