You're right, the first thing any individual should consider when investing in Bitcoin is where to store them, exchange are common for many newbies as they think it's safer to store them there but they're not the best place to store Bitcoin or any other cryptocurency. Private wallet are the best as your Bitcoin won't be affected by any hacking happening to the exchange you bought your Bitcoin from but when you leave them on exchange, you can lose your Bitcoin.
Apart from a crypto newbie who has a mentor who is well educated about the importance of security in the aspect of holding one's crypto asset safe, other newbies who don't have proper knowledge about security will end up keeping their coins on the CEX. That's what most crypto enthusiasts do, but hack issues and the news of not keeping their assets on exchange are the reasons why most of them are not deviating from holding their assets on exchange. I know that this forum is an eye-opener in light of receiving serious warnings about keeping an asset on exchange. When I was yet new in the space, I also held my coin on CEX and even staked some coins on the exchange, but I am now very aware of the risk.