Bagging clippings is a pain,you have to dump the bin out every few passes if the grass is tall & thick,and I've seen the piles of dumped clippings start themselves on fire when they decay too..
Weight of the bagger bogs the tractor down and can take life out of the transaxle if its one of the weaker ones many use nowadays..that may be why one isn't offered as a factory option..
As noted ,the clippings make for good fertilizer too..
If you mow often enough,clippings wont pile up and be a problem..
On the tractor forum, a lot of guys bought AG tread tires ,and soon learned they work great in soil,but in snow they are no better or maybe worse than chains on turf tread tires..
AG tires are directional tread and as noted above,backing up can be impossible at times,they only grab well going forward...
I had a pair on my plow tractor and I could push snow as far as I wanted--but I'd have to get off and PUSH it to back it out half the time,with the tires spinning in reverse..chains don't work on them either unless you get the "X" type,regular ones just drop between the lugs and dont help much..
Many of the guys who bought AG's went to soft compound ATV tires and found they were much better,the lower pressure and softer rubber makes a big difference in traction..also using 4 or 6 ply tires ,overkill for a garden tractor or riding mower,actually makes for less traction,the tires are just too stiff,but do resist punctures better..