Where do I start with responding to this... let's begin with the uncharitable tag at the end I think.
You might not want to read a long response so here's the short version: this post is advice from one creator to another that what they are doing is not working, and I am trying to get people to think about why it isn't working and what they can do about it by presenting a way they can put themselves in their audience's shoes through the similar scenario of being the audience of a youtube video. I am not telling people to "bend over backwards in order to be nice to [their audience] to 'earn' their payment".
As you can see, ~74% of people will not be swayed to reblog a post that they weren't already going to reblog just because you told them to, no matter how polite and friendly you are about it.
And here's the thing, if you look in the notes of the post the comments/tags on it are all like this:
An absolute chorus of people saying "telling me to reblog your art makes me not even want to interact with it".
Thus clearly, it's not working. Setting aside the imperfect nature of tumblr stats, that's still a very significant amount of people who have voted on this poll and said they won't reblog a post if you tell them to.
So. I am not saying people need to "bend over backwards [...] in order to 'earn' their payment". I'm trying to explain why people are reacting like this—if you forget the humanity of the person on the other side of the screen and start treating them as a number that could be going up, you're going to alienate people and push them away—so that people can change their approach and actually get the result they want.
Or, in very simple terms: People don't like being told what to do. If you want someone to do something, you need to make them want to do it. Telling them to do it is not the way you do that.
Also secondly this is getting way too long but it does need to be noted that there are several ways that likes contribute to getting posts seen, such as "based on your likes", recommended posts in general, and the "more posts like this" section that shows up in several different places on tumblr.
Thus, reblogs are in fact not the only way that posts get spread on tumblr nor are they the only contributor to the post ecosystem.
And indeed, if I take a look at the reblog graphs on my art, I might have a lot of reblogs on a post but they all terminate after that one reblog from me. Because most people on tumblr do not actually have followers, and thus reblogging posts is a way for them to interact with me and not a way for my posts to get more traction.
This is easy to forget if you've been on the site for a decade especially if you've been on the site for a decade making posts, especially posting art, but unless you have a highly specific themed blog, or you're a social butterfly, it's very common for people on here to just not have many followers at all.
Those 3 big clusters are all me, one is the original post, and the other two are self reblogs of it. There's a few short reblog chains that happened, but you can very clearly see that the vast majority of reblogs terminate the reblog chain there. Evidently, people are reblogging the post, but it's not spreading further because that's just not how it works.
Anyway whatever if you take away one thing from this post it should be this: if you want to encourage a particular behaviour in your audience, you need to think about what it's like to be your audience and then treat them how you want to be treated. Simple as that.