This never occurred to me as a topic because I have been running racks of my own servers for over a decade.
I was talking to a friend last week who was about to scale his business up dramatically. I asked him about his hosting and he was on a $30 per month unlimited hosting plan. So I read the fine print of his contract for some pretty eye opening “limits” on his “unlimited” plan.
Needless to say my friend is now setting up a dedicated server to ensure his sites and clients will have flawless connectivity. My advice is to read the fine print is you are planning to scale up.