This is interesting and it has satisfied my curiosity that there is no much danger of cheating the exchange with multiple accounts unlike as it is with casinos.
So the exchanges that prohibit multiple accounting are being unnecessarily strict.
Exchanges do also offer some kind of bonus, you know? And them allowing only one user to one account could also be a result of that bonus, or it could be to follow regulatory compliance.
If I may ask, why do you own up to 4 accounts in the same exchange? Any special benefits?
If you are a trader, you might need more than one account for different trading purposes so that you can stay on track checking your trading activity. Some people have accounts dedicated only to spot trading, others to futures trading, and other forms of trading activities.