So I’m assuming you’re talking about the safer sites (non-ghost, etc).
There’s really no need for cargo scanners as you’ll rarely encounter an empty can. If you’re quick at hacking you’re not wasting too much time by not cargo scanning and you might find better use for that extra mid slot than you would save time in using a cargo scanner. In other words, it’s a subjective choice. Personally I don’t bother using a cargo scanner in these sites but that’s just me.
Also - I rarely encounter partially-picked sites, so while I agree it can be a nuisance, I don’t think the removal of cargo scanning is going to change the fact that if someone wants to be a prick and keep a site from despawning by leaving an unhacked can, they’re going to be a prick with or without cargo scanners.
Perhaps a better solution, to discourage partial cherry-picking, would be to have a timer countdown from when the first can has been hacked, and the site despawns when the timer expires. Of course, this would introduce a situation in which said prick might want to constantly despawn sites by hacking one can and leaving, so to mitigate that the timer would have to be somewhat lengthy (say, an hour) and a new site would have to respawn shortly after the despawn in the same or in a nearby system.