Less time consuming that a full shim. Some people think they can cause the end of the fret broad to hump, and maybe they do after 15-30 years. But you’re talking about shims that are less than 1/16”; a 1/16” shim is huge, and can get you almost another 4/64” of action out of the saddles on a bass. The other advantage is you can learn to work on your own things instead of spending $100 and waiting 2 months for someone to do the same thing. There are still a ton of 70s fenders out there with the micro tilt necks which are a lot less stable than a full width partial shim.
You really just never know what you’re getting anymore. I’ve seen $2k american ultras need neck shims, I’ve seen $400 generic basses with neck pockets so tight you have to lever them out, I’ve seen $3k martins that won’t play out of the box.