Rather, financial prudence lies in keeping only an optimal number of credit cards, rather than way too many of them. Yes, “optimal” in this context may well be a subjective term but fact of the matter is that 2 to 3 different credit cards are more than sufficient for any individual entity.
One of the foremost reasons for which we discourage having too many credit cards is because it is tough to keep track of payments as well as due dates on them. Otherwise, when you have say just a single or 2-3 credit cards, it is relatively a lot simpler to keep track of payments on them. That way, you can also be prepared when the payment is to be made, and once done in time, can avoid penalties like late fee, which the banks are more than happy to levy in case the repayment is made after the due date.
Another very important reason for which too many credit cards are always discouraged is because one tends to borrow way more than what is suitable, often by effectively ending up “maxing out” on all the credit cards. So for instance, if you have 6 credit cards with a combined credit limit of $100,000 and you max out on all of them, while having an annual income of $100,000 at the same time, it is but natural that you would repay back less than the total outstanding dues on the cards, effectively incurring heavy interest outlays.
All this can be avoided by maintaining discipline and sticking to a few cards only. Remember that even with those few cards, most major expenses can be met with reasonable ease; with more cards, there is always the temptation to purchase things which you simply do not need and ultimately will have a lot of trouble in repaying back to the concerned banks.