There is nothing wrong in a gambler having more than one casinos they play on, Infact, a gambler can have up to 10 different casinos where they Gamble on respectively. There is absolutely no harm in this as long as the gambler is able and capable of managing his accounts on this casinos well, and as long as the chosen casino are all reputable ones.
Of course, everyone is entitled to their choices, but I see this as the greed of not letting go, wanting to have the taste of every casino which I am certain that they can't keep active at the same time. If a gambler has 3 accounts, I believe it is okay for such gamblers as others are only excesses, and there is no benefit that such gamblers would ever want in their casinos and sportsbooks that can't be derived from 3 accounts if they are better selected. Moving it to 5 accounts is still somewhat reasonable to me, but having 10 accounts? That is excesses and I know that no one can be able to be gambling at the same time in 10 accounts, not even you if you are sincere with this.
The gist is that those who would have 10 accounts will only be wasting them as they will never be able to keep them running and they wouldn't want to keep their money wasting in all of them, so they seldom fund them. Don't you even think how this will be stressful? Login in 10 different gambling platforms simultaneously daily? This is work on its own not to talk of gambling there actively as well. I wonder if gambling is what the person wants to use his entire time of the day to do, that can only be what will encourage such. I only see this as overbearing for gamblers if they do it, and most will just want to feel a service or partake in bonuses and later abandon most of these accounts, that's the norm for it. Besides, this is the reason why those who are looking for more gambling accounts get to meet a lot that will treat them badly when they can't be satisfied with the good ones they already have.