What is the thought process behind people paying someone to DM for them?
I mean, I think if you read the thread that becomes relatively clear.
Common reasons to choose to pay for a DM (many of which we've touched upon) are 1) wanting a game at a particular time that works for your schedule; 2) wanting a DM who is
less likely to be flaky, unprepared, etc. and a game more likely to actually happen consistently; 3) perception that the paid DM may be more "professional" and/or higher quality; 4) needing special accommodations that it is less uncomfortable to ask of a stranger you are paying to be accommodating than one running a campaign for free; 5) being a long term forever DM (something which means that even if you assemble a whole new group, guess who quickly proves to have the most experience in that group and is the natural person to DM), 6) a streamlined group finding process through startplaying, roll20, and probaly some other service I don't know; and sometimes yes, as you seem to assume is the main reason, 7) having limited free options in your area.
On this last point a lot of the paid scene is online, so really it's online free games which are the point of comparison, and if you've had good experiences great, but I think a lot of people land on paid games having had a lot of frustrating ones.
There are, of course, paid in person games as well, but I have no first hand experience of those. I think a lot of them I see in my area for like $10 a head are mainly just paying to cover a venue's table fees and maybe pay for the DM's gas or drinks or whatever. But there are certainly people on the other end of the spectrum, running games as premium experiences for the well-heeled at a castle or something.
As for the vagueness in my list above about where paid DMs actually are more skilled, more professional, etc., sadly paying someone is no guarantee of that, but if they are a mature and responsible person (a BIG IF), I do believe it increases the likelihood.
