I have my car key on a clip that allows it to be removed,
dont like things hang off the car key as the weight can damage the ignition barrel..
I was told that many, many years ago but that was when keys seemed to be softer metal so the key would wear.
Then keys seemed to improve & the barrels then started wearing. (and you had a situation where older keys were used to gain access to older cars (and in the case of Fords, that meant cars of only a couple of years - one of the guys at work owned a 2 y/o granada, top of the range, loads of bells and whistles for the time. He locked his keys in the ignition. I used the door key from our 3 y/o transit to open his drivers door. He spent money installing deadlocks after that))
Either way, it cannot be good to have all that weight swinging around uncontrollably off the end of the ignition key.
And, of course, although the collection might not in itself weigh much, when you use laws of levers, that weight is swinging around a point which is a good inch away from the point at which the ignition key is fixed in the barrel - so multiplying the weight.
Of course, the act of inserting / removing the ignition key must also cause wear and tear.
My bunch of keys consists of house, locker, padlocks, clubcard etc but the car key is not on the split ring, it is on a quick release so it can be used on its own.