You read Hacker News, which means you probably know more about computers than at least 99% of the population, and far more than 98%. Seriously, consider that.
Take something you don't know about. For me it's cars. If prevailing wisdom was that unless you bought some $40 item for your car, it could easily be stolen, you'd probably buy it right?
This is what people are told: Windows is insecure and anyone with a clue can just steal your credit card number. I know that if I just don't install crap from the internet, and have a reasonable firewall, I'm not going to get a virus. I haven't had antivirus in over a decade, though I've run some web-based ones on occasion to check, and have never had a problem. I know that, and you know that. My dad (who is much closer to the other 98% of the population) doesn't know that.
(As for corporate use, you answered your own question. IT staff installs it for no reason other than to be able to prove to their boss that it isn't their fault when stuff goes wrong. )
For the IT staff, the fact that your computer slows down is an externality; it is not their problem. If the anti-virus can catch a few viruses and doesn't result in many help-desk tickets, then it makes their lives easier. Cleaning up a virus is a tedious task, as even a simple re-imaging can take a while, and that's if you can use a standard image.
They also don't know how smart their users are. Some of them are great, and might read HN, but others will go download any game or smiley pack they can find.
If IT staff were paid based on how smoothly the computers run, they might have a different opinion. Their current goal is usually just to make sure it runs at all.
> Their current goal is usually just to make sure it runs at all.
Indeed. I'm the lead of the "IT Staff" at a small non-profit (~70 users) running mostly on second-hand desktops. Two-thirds of our staff is unpaid, usually interns who are here a few days a week for 3 months, and then they're gone and someone new takes their place. Training proper computer behavior is hard.
So... we run A/V (not McAffee), because we have to. We also lock down the systems hard, not because I think that's a nice thing to do to your users, but because we have to. Imaging all these different desktop models is difficult, and we have very limited resources for doing re-imaging/re-installs/virus cleaning/whatever.
My goal is to enable you to sit down at your computer and be able to perform your job. A 20% performance hit on all computers is worth it if it means that 20% of the computers aren't down for maintenance. :)
There are a couple of ways to address the virus problem besides installing anti-virus on Windows.
Here's a few things I'd consider if I wanted to run an office with minimal computer support:
- run the LTS Ubuntu instead of Windows
- maybe run OS X, on Mac Minis if buying new hardware
- install one Windows terminal server for critical Windows-only software
- lock down firewall to permit only whitelisted web-sites
- run locally hosted (I believe this is possible) Google Docs as office software
Windows virus problems, people surfing Facebook, porn, you-tube, Twitter etc., will suck away time in an office if you don't get some kind of a handle on it. I hate offices where stuff is super locked-down, but put in charge, I'd want to screw things down pretty tight.
Obviously developers, salespeople might be somewhat of an exception... it's a hard call to make.
Take something you don't know about. For me it's cars. If prevailing wisdom was that unless you bought some $40 item for your car, it could easily be stolen, you'd probably buy it right?
This is what people are told: Windows is insecure and anyone with a clue can just steal your credit card number. I know that if I just don't install crap from the internet, and have a reasonable firewall, I'm not going to get a virus. I haven't had antivirus in over a decade, though I've run some web-based ones on occasion to check, and have never had a problem. I know that, and you know that. My dad (who is much closer to the other 98% of the population) doesn't know that.
(As for corporate use, you answered your own question. IT staff installs it for no reason other than to be able to prove to their boss that it isn't their fault when stuff goes wrong. )