I seen many bitcoin split.
you are looking but not seeing.
these things you listed here are not "bitcoin splits" these are bitcoin "proposals". there can be a thousands of them and there are many actually available, but them existing doesn't mean bitcoin will split just because they exist.
on top of that the chances of bitcoin splitting is very small. because first of all bitcoin is too big to split, there is a lot of money at risk. not just money of investors holding bitcoin but the money that miners invested in their mining farms and equipment and all the contracts they have such as contract with electricity companies and all the bills they have to pay....
secondly majority of bitcoin ecosystem is supporting 1 thing and 1 thing only. and when majority is behind 1 thing there won't be another chain.