I do see bikes left around sometimes, but only a couple. I haven't seen that with instruments and slablets. One thing you could do, if you just want to be rid of the clutter: testingcheats on, shift-click the item, and Destroy Object.
This was a huge issue with clay lumps for a while, until they finally toned it down. Every park bench would be surrounded by a ring of abandoned clay lumps.
I also use this method to destroy bikes when my sims are in the jungle. I never buy bikes, but sometimes they end up with one from somewhere, maybe dumpster diving, maybe a Winterfest or neighborly gift. If you tell you sim to go through an archway in the jungle and they have a bike, they pull out the bike and get on, get off and put it away, pull it back out, and get stuck in that loop. Cancel the action, destroy the bike, now, GO THROUGH ALREADY!