Uncle Billy:As a practical matter, daytrading in a cash account is difficult to accomplish. This is due to the application of two related rules known as "good faith" and "freeriding" requirements. These rules are not part of the PDT rules and stand on their own. In summary, vastly oversimplified, these rules require that you have all the money you need to settle trades in a cash account available even if the stock is sold before settlement. Moreover, and herein lies the rub, the good faith issue arises when the stock is sold prior to settlement even if the customer funds the trade subsequent to sale but prior to settlement. The freeriding provisions kick in whenever funds are not available on the settlement date. There are numerous discussions of their application on the internet. Reading some of the examples that are provided will likely cause a person to realize that compliance might be more trouble than it is worth.
After re-reading what I could find online, I am in agreement with Uncle Billy. Here is my interpretation as an amateur trader: You can indeed get in trouble if you trade too often in cash accounts, but it's not because of the pattern day-trader rules. It's because of the T+3 rules which will quickly reduce your buying power if you trade frequently.
Then, if you upgrade to a margin account to avoid T+3 settlement restrictions, then you are subject to the PDT rules. If you have a ton of cash and a plain cash account, you could probably daytrade all day. But most people don't.