Because most people - like broadband uploads vs downloads - don't write a lot, only read.
This is not a server tool. How much writing do your home PC's do? Basically what you've downloaded and created that day, and that's it.
If you're assuming 10 year life, and downloading, say, 15TB a year, that's 15,000 GB or thereabouts, which is over 1000GB a month - I'll be more impressed with your Internet connection than where you're storing it all. I have a Steam account with 1000 games and it doesn't approach that kind of space. This is basically deleting and redownloading every game I own every single month.
Or your creation ability if you're churning out 1000GB a month of user-created content. Maybe video, but then you'll probably be better off with a more professional setup than one SSD by the time you get to that level of content-creation.
And, don't forget, reads are "free".
This is perfectly adequate for a consumer drive. No, you wouldn't want it in a 24/7 RAID5 config on a server. But then, if you did that, I'd call you an idiot just for trying that in a limited write-life device. This is not a server drive. This is a consumer drive. And for that purpose it's absolutely fine and way out of most people's reach, even most IT professionals.