Tire performance, as well as added suspension, as well as fewer flats. Someone mentioned they've had 1 flat in 4 years.
One flat in 5 years for me. But it has to be the right tire.
When I first went tubeless about 5 years ago, I went with UST Michelin 2.1 XCL's and they were crappy and I'd get huge tears in the sidewall. However since then, I've heard they've made improvements and I've heard nothing but raves from Mich users.
Last spring to change up I tried a pair of UST Hutchinsons, Spiders I believe, and they were the pits; flatted twice in 5 rides.
Like I said, on one bike I have UST IRC Serac 2.1's and have had one flat in over five years where I made a 2 inch tear in the sidewall squeezing between jagged rocks where I would have demolished ANY tire. Cycle Craft usually has the Serac's in stock.
On another (probably would consider to be my primary bike), I'm running the classic Panaracer UST XC Fire Pros 2.1 and have NEVER flatted (as he promptly knocks on wood) in over 2 years. Town Cycle and Campmor regularly carry the UST Fire Pros. I use Stan's in my primary rides' tires as insurance.
I've heard all the horror stories of tires 'burbing' and unseating on high speed turns, going flat overnight or mid-ride etc. and I just scratch my head...if you use a UST rim with a quality UST tire I can assure you, you won't have any problems, will be able to run your tires at lower PSIs, and in every eventuality, will not suffer a flat for a long time. Yes, I do carry a tube with irons in my C'bak but I have to thank whoever brought it up because in all honesty, I haven't seen it literally in years so I wonder if it's still in decent shape in case I do ever have to use it.
I'm no flyweight (bet. 190-200#) and I ride the same trails you do (RW, Skyline, Waway, Blue, C. Rock). No problemos...