They wrote their own because it's more fun to do that, and also because they really wanted me to win. The computer is really really bad
The main problem is that I only win by having my extremely-stupid blunders overlooked and then spotting my opponent's extremely-stupid blunder, so if the computer never misses my boneheaded blunders and also almost never commits any exploitable-in-one-or-rarely-two-moves blunders of their own, I can't possibly win, zero chance.
It reminds of a reversi I made for a school projects: users liked it because the computer was so bad that they could win..