Tldr people try to game image recognition, word filters, etc to increase visibility of their post on social media. It works.
People are slaves to the algorithm, even if they claim to not care. If you alter your post to increase visibility, you are playing by it's rules.
By censoring even potentially blockable words, not only are they improving the odds it will go to a wider audience, they get people to comment "why is that word censored/why is there a random dot/erase spot?" which drives up engagement stats, thus sending it to even more people.