The reason why plating gives gold is actually to reduce the effect of team-wide snowball(the "deathball" meta)
If a botlane gets a gank and win 3v2, sure, they will get 1-2 plates(2 plates give 320 gold total, which is less than a kill gold+2 assists) but the armor on tower will prevent them from destroying that tower fast. Also, by taking plates, they are wasting time they could use to take drake(that, in my opinion, is worth much more than 320 gold), roam mid or just recall. If they win lane, they can't really go roam because their enemies will just take their plates instead.
The idea is that winning a lane is just winning a lane, the winner cant just go win all other lanes. This makes lanephase a bit longer, with more chances to comeback, either by outplaying or with a jungler's help. Remove it, and there will be no point in staying on your lane, and slightly winning team will just group as 5 to run over objectives without anything losing team can do