That sounds like the result of “cleaning cookies” rather than the solution…?
The most basic example is recommending the clearing of the browser cache. It’s there for a reason, and by clearing it in 99% of circumstances one is actually harming browsing performance by forcing the browser to re-load content from the net that it could have loaded from the cache.
The clearing of app-related recent histories is also functionally harmful and from a performance context it’s utterly pointless. Admittedly one way that CCleaner distinguishes itself from the million-and-one apps out there that claim to speed up your computer and all they need is your credit card number is that CCleaner (to my knowledge anyway) doesn’t explicitly claim that its features improve performance, but it doesn’t need to because that’s what the layman believes it does by implication.
The fact that there’s a “driver updater” when those can very obviously harm the functionality of a PC (and I’ve seen AVG’s driver updater do it twice). But obviously Piriform – the king of “we’ll improve the performance of your PC, we just need your credit card number” scam – very carefully vetted every single driver they recommend for every single PC configuration, right?