For my needs an Air would work as well as a Pro, so why not go for the lighter one if I had to carry my computer around all of the time? I'm a sucker for small, compact notebooks though and adored the 12" G4's back in the day. The 14" MacBook Pro I have now is the largest main laptop I've ever owned.
I don't find my 14" excessively heavy either, but I have a friend who returned his 14" M3 MBP because he found it unacceptably heavy having switched from a 13" HP Probook that was almost 1/2 kg (1 lb) lighter. I made fun of him for it, but weight is important to a lot of people.
I guess the flip side of this is:
If the weight difference isn't much, why not go for the 10x better screen, way better speakers with spatial audio support, additional type C port and SD card slot.
The screen and speakers are really a lot better. Sure, if you find the weight difference more important, i can get that (but really, it must be some pretty specific requirement), but if not.... the screen comparison is a truly case of "this is a decent SDR display" in the Air vs. "This is one of the best displays i've ever used or seen on a computer that has full HDR support".
If in doubt, view some HDR content (e.g., movies - even trailers out of Apple TV or search youtube for "4k hdr" and make sure that the display is actually switched to hdr mode and the browser is playing in HDR - this should be automatic if the browser detects HDR content) in the store to compare. A large part of what I and (i guess many others) use my laptop for is media consumption on trips. The screen and speakers are just next level vs. any other laptop, period.
If you don't do media consumption, fair enough - but if you do - please, please make sure to watch some HDR content on both machines to compare. Because just looking at web pages and productivity apps doesn't show the full difference between the two displays.