Funny you should say that - I was doing that for a while, but was soon hitting the memory limits set by the providers in the resellers end. I have built sites for several businesses which generally serve static content (No problem there), but do have a few that have pretty good levels of content and rather large databases, one being a 5k product e-commerce store. Not that the scripts take up memory so much, but the overall combination of everything going on (12 sites), it was starting to cause stress with the providers. The eCommerce store stakes up about 400mb Ram steadily. With the rest of the sites taking up about 200MB total.
I know I could have gone with groups like inMotion Hosting, Hostgator, etc, and gotten some better hosting there in terms of memory allowances, but with the budget being what it is, I went with VPS. One thing I have found is that a lot are using Cloud Linux. which is great. But, if misconfigured which I seemed to be getting, was actually throttling down my whole hosting account and not just the sub account I had set at the time as a reseller.
Also, I have need of about 2 Dedicated IP's just for SSL's alone. With PCI Scans, site compliance etc, at least a VPS is given favor over shared reseller hosting. Technically, I am a shared hosting provider and the sites I have are on a shared server, but they are not shared on the same container as the hundreds or more on the same server, so security is greater. Plus - if the need should arise to go dedicated, I will have a heck of a lot more experience in this area than say someone who goes from shared/Alpha Reseller to Dedicated and has no idea what to do with the bash shell.
A couple of decades ago, I cut my teeth in shell access in the days before Windows 1.0. I would hardly call it as sophisticated as it is today, but there is something to be said about having some extra low level control over the server when you need it via the SSH.
You don't always get that with Alpha Reselling or whatever flavor Resellers accounts you may want to purchase.