Ok I'm a little sick of this and I want to clarify this for the sake of others who want to make money with their art if you take the time to read this.
First off when you ask an artist to do free art, you are asking them to take a portion of their own personal time to make you something. Even if it was something that would take 5 minutes, that's 5 minutes could be used to do something that would benefit the artist.
Now I'm also not saying I'm against doing free art 100%, cause I see the uses of it in things like making a gift for someone or it could be a donation towards something. Now when I say gift, this is generally with people I know on a personal level, or it might be something I throw in with a frequent commissioner as my way of saying thanks for commissioning me instead of another artist.
Personally for me, I like spending time with kids, some kids like watching me draw and ask me to do things like "draw Sponge bob" something like that I'll do because they just want to see draw and I'm already taking the time to spend time with them. Now if one of them wanted me to make some really impressive Sponge bob art that had Sponge bob go jelly fishing in bikini bottom, no I will not do that.
Second, it's an insult to the artist saying that they aren't worth paying to do art for. Artist that want to make a living or money off of their work spend lots of hours practice their craft, you may do things like watching YouTube vids, playing vid games or maybe hanging out with people in that same amount of time.
Now it sounds pretty cutthroat when I put it as "they aren't worth paying" cause that's what it sounds like to some artist that want to make money off their art, when you ask for a request, you are basically saying that their time isn't precious and its ok for you to spend the same amount of time indulging on other things you want to do with that time. Now maybe its different, maybe you like their art so you ask them to do a request for you. It comes back to this point, you aren't paying them, so what benefit does the artist gain from you simply saying "thank you" at the end of it? There's that saying "a picture is worth a thousand words", doesn't sound like a fair trade to me to trade two words for a thousand words if you want to look at it like that.
If I had to put it in another perspective, imagine you work at a place like Target, you have been contracted to work as a cashier for about two weeks, in those two weeks while you are working you are also looking for another job to take while working as a cashier cause you know you won't have an income in two weeks, for a lot of artist that's basically what it looks like, trying to get another commission while working on other commissions or practicing their craft, on top of that you are asking for free art while some are very much neck deep in the amount of work that needs to be done.
I'm not talking about myself when I wrote all this, cause truth is way to many people take for granted that artist spend time to better themselves and forget that an artist's time is as valuable as anyone else's time. In fact I'm probably the worst person to use as a model for the examples I've used, I'm talking about those artist that bleed and breathe art 24/7, or artist that really want to make some money on their art and take it seriously. I take being an artist seriously and I don't like using my time for a stranger unless their in an intensive to do so, sounds greedy to some but, time is money, and money is an essential evil we use in our daily lives.