There are thousands of years of history behind the cemetery tradition, part of a culture that's dominant in certain parts of the world. That there are other human cultures which have different practices doesn't make it any easier to change that one.

Not really thousands of years, western burial traditions have changed a lot over time. Here are some of the other examples https://commons.m.wikimedia.org/wiki/Tombs_by_type

It’s an interesting subject with a mix of practical, religious, and economic incentives resulting in a huge range of different outcomes in even closely related cultures.