That sounds like a great way to teach numbers.
I play UNO (cards) with my daughter, yahtzee for probabilities and the like - she loves it. Games used well are perfect tools and I love that you designed some with the kids - it makes them part of the creative process - the numbers are "theirs".

I used to like maths as a kid and never really understood the it's not useful argument. How are people supposed to design and build all the technology we use without maths?

It is a visualization thing. I can't visualize the numbers into something practical (at the higher levels), so regardless of me knowing that it is necessary, there is no mental connection for me. For other people, they can "see" the numbers differently - school favors them.