>>530337885
Several reasons
1) attempting to hook has several ways where the survivor can be saved, effectively being the same issue you mentioned as slugging but worse.
2) Carrying the survivor slows you down but also wastes 4 seconds every time to pick up and hook. If the only hooks around arnt directly towards where you would be going anyway, it wastes more time than you think travelling there then back to whatever gen you want. If a survivor was nearby, you basically gave them 10 free seconds to do whatever they want while you cash in.
3) Many survivor perks trigger off being unhooked. Hooking them means they may be able to heal faster, have I-frame parries next chase etc. While there are powerful anti-slug perks, there are far fewer compared to anti-hooking perks.
4) Its far easier to redown a slugged survivor than an unhooked survivor currently.
5) In endgame, if theres three or more survivors, they can get the 4th out risk free if they are hooked, so long as they are co-ordinated. They cant do this if the person is slugged, unless they are running a certain perk
6) Some killer powers are punished for hooking and incentive slugging. Oni for example ends his power when he picks up. Plague's power still loses duration while she is carrying. Twins has to waddle all the way over to where victor is to hook when they can just keep using victor.

The key point is slugging when you know other survivors are near builds pressure faster than anything else and killer is all about building momentum. 2 downs > 1 hook. You dont slug all the time, but you SHOULD slug when survivors are clumped up.
Sometimes you NEED to slug because they have a guaranteed save if you pick up.