While I can't speak for him, in my case it's because I want my predecessors to reap the benefits of their labours and spend their money on themselves before they die. As I say to them (and others), you only get one life and there are no prizes for checking out with money left in the bank.
I had this conversation with my parents recently as I share a similar view to the parent comment. My father has made a decent amount of money from his successful business, but by far the greatest proportion of their wealth is tied up in various property assets. They put this fortune down to good timing vs being "earned" in the same way as the business profits, and believe it should be something that future generations in the family benefit from. They travel internationally multiple times a year and assure me they will continue to enjoy the good life for as long as they can, but they're adamant when it comes to their plan to leave a meaningful estate for the kids and grandkids.
