Using and leaving your assets on exchanges is the same as using a bank; aren't we all in crypto to have complete control over our money? So, what's the point of keeping it on exchanges?
I would not agree that it is exactly the same thing, because in some countries client deposits in banks are insured by the government, so although I don't know if that amount varies from country to country within the EU, but in my country that amount is EUR 100 000. I don't think any crypto exchange has anything similar, and what I know is that they have secured part of the client's funds that are in fiat, but if a big hack happens, the only thing clients can hope for is partial compensation, and that after probably years of waiting.
The reason why there are so many coins on exchanges is that people mistakenly consider them to be crypto banks, but also because of the ease of trading whenever someone wants. CEX encourages this in some way because they have implemented a withdraw/service fee which is not very cheap, especially if someone would withdraw and then deposit their crypto assets every day.
No hardware wallet is the ultimate solution, regardless of who produced it and what its specifications are. The only thing that leads to ultimate security is a properly created cold wallet, everything else is more or less an illusion of partial security.