Well, its very simple, that many shared hosting providers struggle with providing a good service, even though if they keep a good ratio of client to the server resources it can still be good, but so many of them oversell their resources, which cause bad performance on shared hosting platforms, also if your website needs grow then surely there can be a limit to each shared hosting provider too, even nowadays many people over sell VPS too, so a bare metal is always a best choice, where you at least know that you own the hardware and getting full resources of it.