>>unless my eyes decieve me, almost all computer monitors are 17 inch and 19 inch LCD's.
"Almost all" is a big overestimate. I would estimate that 60% of NEW monitors are 17" or 19" non-widescreen LCDs, about half and half of each. But the majority of monitors currently in use by gamers are old ones, most of which are CRTs, though LCDs are replacing them at a steady pace. Furthermore, most of the widescreen solutions which require manually adjusting the FOV are either based on the Unreal engine or Quake III engine, which debuted in 1998 and 1999, respectively. CRT use was even higher back then.
>>And even out of the extremely few CRT's still in mainstream use
There are LOTS of old CRTs still in mainstream use, just not so many still being sold.
>>most of them are 17 inch and set at 1280x1024 resolution (even though the screen is physically 4:3)
Every 17" CRT I've seen has a recommended resolution of 1024x768. A game running at 1280x1024 on a 4:3 screen will be distorted no matter what the FOV is.
Well maybe things are different where you live but I haven't seen anyone use a CRT monitor in years, except for this one guy I know who still uses a huge 20-something inch one that's really nice. And yeah, 17 inch CRT's have recommended resolution of 1024x768, but no one knows that or cares. Most people who had 17 inch CRT's had them set to 1280x1024 because that was the highest that Windows would let them go. I've never seen anyone use a 17 inch CRT at 1024x768. Sure, it's the best resolution for those monitors, the average person doesn't know stuff like that.