Same reason one field strips any firearm for maintenance? How do you propose one adequately clean & lube it, otherwise?
There are numerous firearm designs that can be adequately cared for under normal conditions, without field stripping, or full detailed stripping. There are numerous firearms that have been in use for over a century and have never been taken apart, even once.
There are some made to be taken down, part way, as a regular thing. There are others that are made to be taken apart all the way, without problems.
The whole "guns must be taken apart and cleaned after each use," was a valid mantra for CENTURIES. From the beginning up to the age of smokeless powder and non-corrosive primed ammo. It is a powerful historical imperative, and tough to argue with.
Except for when people repeatedly take apart things that weren't made to be repeatedly taken apart. OH hell, I been doin it that way for 20 years, never no trouble...until one day.. and that pin don't fit so tight anymore...that round hole is now a bit egg shaped...things seem a little ..loose..etc.
Some guns are about immune to that, some, aren't. Why risk it if you don't need to?? detail strip that 1911 every day, and twice on Sundays and it will still probably out live you. A Ruger .22? Can't say with certainty, all I can say is I'm not gonna find out, not with my pistol, anyway.
And yes, though it took nearly half a century, I've finally learned the wisdom of "if it ain't broke, don't FIX it!"