I think all graphic design gigs I bought here had an extra to purchase if one wants the source file, or a package that included it. In some case, I didn’t need it, so I didn’t buy it, in other cases, I knew I might need it, so I bought the extra for it. (Take note of the “I knew” here, you can’t count on all buyers knowing stuff related to your gig, so you better be clear and mention things, even if you think, everyone should know, that’s often not the case, as pros, we are so involved in “our thing” that we sometimes forget that what’s clear to us might not be to others.)
It’s nothing nefarious to want a source file but it’s nothing nefarious either to charge for it, and from what I’ve seen, it’s very common, yes.
What’s not common though, is, to not give a customer the option to buy the source file as an extra or within a more expensive package because in many if not most or all cases, a file that can’t be edited, won’t be of much/any use, depending on what a buyer wants to do with it.
Some people only want to place a small order at first too, to check if they’d be fine with the result/the experience of working with that seller, i.e. place a test order (which is what many people on the forum advise unhappy buyers to do, by the way), and for that, a very basic offer without source files probably would do fine, it did for me on one occasion.
However, if you don’t want to include your source file in your basic/any offer, make sure that your gig is very clear about what a buyer will get when they purchase from you to not leave room for misunderstandings, and if you want to offer the source file with any or all of your gig tiers, ideally explain why they might/probably will need it sooner or later, so they are keenly aware of not being able to change the size if they don’t buy the gig extra or the package that includes the source file, for example.
Of course, many people don’t seem to read before they buy, and especially with gigs of the 3-tier setup (basic/standard/premium), you’ll get people who want and expect the standard or premium offer which might include the source file but pay for the basic offer which might not. That can’t be helped, though, beyond making it as clear as only possible in your gig setup, unless you offer it with all packages, with the according price you’d want for it.