Some up-dates are to correct bugs, some are "Enhancements" but some are security fixes.
The bad guys are always finding new ways to do their nefarious deeds and browser developers have to keep finding ways to foil them. If updates only came out monthly there'd be quite lengthy periods whilst the threat existed but you wouldn't have the protection against it.
131.0.3 for instance has a couple of bug fixes, the ability to drag List All Tabs off the screen (an enhancement) and a security fix.
