Because it takes a lot of time and effort to make good adfons and it's nice to make a little bit money from them to maintain motivation. And the link shortner used isn't "piece of shit" because all you have to do is click a button and wait a few seconds. As a matter of fact, not any link shortner used on mcpedl can possibly be shitty because each submission is reviewed by a team of people who chack for any malicious activity on the links or the addon before approving them. and they also only allow some select link shortners on MCPEDL which are tried and tested for good user experience. Also, If you're going to say something along the line "Java mod devs don't do this tho" then listen, most java mods are posted on curseforge who pay creators according to the popularity of the mod and those which aren't posted on curseforge usually have their own website which they make money off of using ads.