When the products turns out to have problems, an issue arises between the supplier of the product and the supplier of the fame and praise.
I think that's why people feel entitled to customer service. If the developer fails to provide a good customer service, the users demand refund, that's why it feels very similar to regular customer support.
In fact, the users of the free software can often be much more demanding. Maybe they are rightfully so, since they paid with social capital that is limited, precious thing - unlike money that can be earned in by doing work for a bit.
The pain as a result of the product failure is also the same, it doesn't matter if you paid for it by a monetary transaction or tapping the like button. Even if you haven't done anything directly, you inflated the developers stats - which are the main KPI anyway.
IMHO, if someone wants to make money from their work they should explicitly charge for it. You can't expect to receive all the street cred for giving away your work for free and also receive money for your work. The maintenance is simply, street cred maintenance.
Many years ago I learned my lesson for giving stuff away for free. It's tough to sell your stuff in exchange for a reputation, the demands of the customer never ends. Your part in the deal is also not clearly defined, you are expected to fulfil your obligation by working on every single request no matter what is the scope and if you fail to do that your free users will be mean as if you scammed them.
edit: Sorry for not being able to reply to you all but my account seems to be rate limited. Unpopular opinions have consequences I guess. Shouldn't hold them.