I'm having a bit of trouble with Siri.
If I say "remind me to buy milk when I leave home" it works splendidly.
However, if I say "remind me to buy milk when I leave Dad's home" it asks me when I'd like it to remind me.
I have an address set for "Dad" and can even set this same thing up via Reminders directly, so how do you add a location based reminder for someone else's address?
I'd guess this is because you're asking it to remind you when you leave somewhere, yet you're not currently there. This would presumably require it to first recognise when you are there and then recognise when you're not (again), which is too complicated at present.