Why? It's very easy to get people to plant trees for you. Just give a gardener, even a very old one, some money and they'll do it for you.
Because "caring for the future" is not a problem that's solved with money. Especially when short-term profit trumps it, and the people that should be caring wont be alive in that future and don't give a fuck.
Thinking "we'll just pay someone to do it" is exactly the mindset that fucked up everything.
(And, for starters, you need to care for X to pay someone to do X, to begin with).
No amount of money allows the gardener to plant it in the past. You can pay money now to plant tree now whose benefit will be reaped 100 years down the line. Also, tree is symbolic so no point in going in details of tree growth.