Because most teams have rookies to take up spots or extra depth or they do not have other players coming back in a couple weeks so there is not a situation where you sign a player just to not suit them up.
You keep missing the most important point: anyone from the practice squad they elevated would NOT be suiting up Sunday and then would be cut in a week or 2. So you are accomplishing absolutely nothing by elevating them but spending more money on people who are not eligible to play. The Ravens HAVE the 47 they want to play this Sunday on the roster. They have people coming off IR. What this means is they do not need to waste the roster spot for no reason because again there is no reason.
Lets make this a simple question: what is the benefit to signing a player to the active roster who will be among the 47 on Sunday, because that 47 is already set, and will be cut after? What is the gain?
1. Yes, most teams have the exact same problems the Ravens have. They have guys on IR who will return. They have guys on PUP who will return. They have guys with short term injuries who will miss 3-4 weeks or less. These problems are not unique to the Ravens. Not even in the slightest bit.
2. Are you under the impression that the PS elevations don't suit up when they're elevated? Not sure who told you that, but they lied to you.
In the three games we've played this season:
Jets: Elevated Steven Means from PS to active roster on 9/10. He played 37 snaps on 9/11.
Dolphins: Elevated Raleigh Webb and Daryl Worley on 9/17. Worley played 9 snaps, Webb played 18 snaps on 9/18.
Patriots: Elevated Webb (again) and Brandon Copeland on 9/24. Webb played 16 snaps, Copeland played 30 snaps on 9/25.
So thus far, through 3 games, PS elevations have a 100% suit up and play rate on gameday. In the cases of Copeland and Means, they actually played a fairly high number of defensive snaps. Upwards of 20-30% of total defensive snaps. Webb is pretty much an every snap special teams player.
That COULD change on Sunday, but I'll wait until the final injury designation reports tomorrow to confirm. For certain, if Stanley doesn't play, and likely even if he does, at least one offensive tackle (likely a PS elevation) is getting elevated on Saturday, and they'll 100% dress for the game, because they've made no roster changes to that position since Sunday's game. At the moment, you have basically two healthy Tackles on the roster, in Moses and Faalele. Mekari isn't going to play, and if Stanley doesn't, you need at least one more. So that's at least one "healthier" 47-man player who's going to be inactive in favor of an elevation.
To your last question... there is no benefit to it. Except your question isn't the dilemma the Ravens are facing on Sunday. What you don't seem to grasp is that there's position considerations. Who's the third OT for Sunday's game at the moment? Give me the name of that player on the active roster?