Actual recessed fittings usually don't also have obstructions, but some time they do. that is the use case for these tools. if you need them buy them, if you don't think you've ever seen something of that nature, I'd say there is no hurry to own the (especially a complete set).
The difference is fairly substantial, but also is a function of your other tools. The socket itself is only 4-7mm shorter than a standard unit. Its usually by using the external hex of the socket that you can eliminate the added ratchet height, anothe 11-20+mm of stack height.
Point being that you can save some of that by switching ratchets or socket brands. Especially if you are not already using a 22mm sockets and something like a 10-11mm ratcheat head. If you are using the lower-profile of the standard stuff, you get some extra clearance but its only 15mm or so.