Horse, meet cart.
As the senior IT manager in my company, it falls to me to make sure everything works and continues working, while making sure our trade secrets don't get leaked to our competitors and that some phishing scammer in China doesn't rip off all our employees' and customers' credit cards. If I fail in that duty, I can expect to be sacked and even charged with criminal negligence.
The likes of me are not here to make life easier for the likes of you. My job is to make sure everything keeps working in a stable and secure manner. If you can guarantee to me, from your at least degree-level IT education, that any personal device you bring in and connect to my company network is 100% free of spyware, malware and other unwanted goodies, and I can have it from you in writing that you alone accept full and sole liability for any damages occurring as a result of you plugging your device into my network, I'll let you connect it.
Otherwise, while I bear the responsibility and the liability if something goes wrong, all the users on my network can abide by the rules I've put in place for it, rules which are ultimately designed to protect everyone who works here from both criminals and competitors.