If a trader finds himself needing to withdraw funds from his account for whatever reason, whether for an unexpected emergency, or for some other use, or because it may be his individual preference to regularly sweep his account down to a certain level, he may find himself affected by these daytrader restrictions.
Why people might choose to open various accounts would vary from person to person. For some of them, their strategy of having more than one account, for whatever reason they may have devised that strategy, may be affected by the existence of these restrictions. They can work around it, but having to work around it does constitute "being affected" by these rules.
If you know of any professional trader that derives any part of his living from a cash account of more than 25K, they are still affected by these rules. Less than 25K, more than 25K, makes no difference with a cash account. Cash accounts have been affected by these rules in this way:
Before the PDT rules, a cash account, at least at some brokers, could give its owner immediate access to the proceeds of stock sales. As long as the broker was not providing leverage to the cash account, no one was too concerned that they had to be strict in their interpretation of the three day settlement period. Since the PDT rule however, you have to wait like a lame duck for three business days for cash to appear in your account balance after a sale, because otherwise the broker could be accused of "lending" you money by not making you wait, and thus allowing you to circumvent the 3 in 5 daytrading limitations.
If options trading is part of a professional trader's basic strategy, it doesn't matter if he has more than $25,000 in his account. The options in the account are not included in the calculation of the $25,000 minimum. You could have an account with $40,000 in it, and if you buy $20,000 worth of options your account permissions are immediately subjected to the same limits as anyone with less than $24,999.99 in their account.
Odds are that these restrictions will never directly affect you, Nitro, personally. But they will affect some professional traders, which is what you asked. Even if the extent of their effect is to make a person adjust their strategies to avoid these restrictions, that constitutes "affecting" them.