Money, money, money!
A fuselage which both:
1. takes the stresses of a "not so nice" landing...
2. takes the stresses of pressurization umpteen thousand times...
that's some quite heavy structure. With a considerably wider diameter two things would happen.
1. It would produce more drag
2. It would become much heavier.
Both would mean less payload and less range and more fuel burn, everything else equal.
What you are asking for could just as well be one seat less on each row. That's what they do when you pay a more expensive ticket.
On some planes - for instance the BAe 146/Avro RJ the airlines seem in doubt how many seats they can put on a row, also in Y-class. Some put in 5 and some 6.
My latest flight was on a Crossair ARJ with 5 abreast seating. I looked at it and wondered how the hell some airlines put in 6 abreast seating in that small plane, but they do. That's torture.
If it had been 6 abreast, and if it had been a business trip, then I'm sure that I could have found at least a dozen Danish national laws for protection of worker's working environment which would have prohibited me taking that ride.
But it was a joy ride, and since it was 5 abreast seating and quite comfortable leather seats at quite generous pitch, then it was in fact pure joy.
I chose Swissair/Crossair because they in this respect are favourable to the competition. With my 6'2" that's not unimportant.
Go and do the same. Let the airlines, who operate sardine tins, fly empty planes. And let the good airlines do business with you.
Cheers, Preben Norholm
Always keep your number of landings equal to your number of take-offs