At first Adrian tries because he doesn't want Trevor to feel like he's being allowed to win. And because it's a little bit funny to watch the occasional struggle to remember which bit goes where.

Then he tries because he is, quite frankly, floundering. He was just never interested in strategy. He wants to settle things as effectively as possible and can't really think more than a move or two ahead. It doesn't take long to start losing pieces, and without much regard for their value, either.