The problem is that there are so many different permutations of this that the reminder service (and every other service) would then need to accomodate for hundreds of other scenarios, such as:

- When I arrive at home, turn on the lights - After five minutes, play this song - Lock the front door at 10pm

And then the reminders service (which is a to-do app!) suddenly becomes 100x more complicated than it was to accoomodate all these strange use-cases that are outside of it's bounded context.

It's easy to implement a single use case, it's practically impossible to manually code every possible use case (which would also probably create a huge amount of tech debt).