Originally Posted by
Jughed
Not "any". I know a ton of "serious" cyclists that have not had a bike fit, including myself. Personally, I'm not real sensitive to differences between bikes- within reason of course, and after a few min of riding a different bike - I'm "used" to it. Just like how I'm not really sensitive to small differences in stiffness, compliance and all the other jargon.
Being unable to replace parts is a different story. Bars don't last forever, seat posts can break/get corroded, proprietary clamps/fittings can break, easily in some cases... I'm hard on my equipment and ride bikes till the wheels fall off - for that reason, bikes with proprietary parts - I'm out.
Sensitivity depends on the demand of the ride. I have no doubt you can jump on just about any bike and feel fine on a morning ride, but when you get into a 100km, a 160km, a 200km, a 300km, and beyond, etc; at a certain point, believe me, you're going to get "sensitive".
If you can currently do a 200km ride and feel fine, then a bike fit may allow you to extend that to 250km without any additional discomfort. That's from a postural perspective of course. Your endurance is still your own responsibility.
And if you never do more than a century, a proper fit can still help you enjoy the ride more.