Main advantage is massive reduction in punctures. Using sealant, thorn punctures no longer matter, and as you’ve got no inner tube you’ve got nothing (except the tyre itself, which though possible is much harder and you’d have to be running silly low pressures) to pinch. I’ve taken tyres off to change them and found numerous thorns in on occasion, and I’ve never suffered a flat since running tubeless (8 years now). Nor have I rolled a tyre off the rim, but I’ve always done my homework though…
Secondary benefits… Usually you save a very small amount of weight, though not always. Rolling resistance is reduced, not massively but removing the inner tube removes a slight amount of friction. And you can run slightly lower pressures for increased grip, though most people usually seem to take this too far, and end up with loads of grip, briefly until they then ding the rim or roll the tyre off it! So top tip number 1 if you go tubeless, don’t lower your pressures by more than 5-10% over pressures you’d run if you were running tubes…