Seriously though, something happens out there, from my perspective subconsciousness talks to me, slips notes with various reminders that I utterly forgot for weeks, or makes connections to things I never thought about before. I think it is because its so natural to walk for us, our consciousness is completely free.
And on weed, alone (important part, if I am with somebody my focus is on communication and not some inner voices), this flow of thoughts and ideas becomes so intense that I usually have to stop and start typing them into some notepad in phone, otherwise they will be forgotten within minutes (the curse of short term memory effect of weed).
I've come up with at least 20 different startup ideas among other things, some entirely out of software engineering (my daily job). Some of them look a bit moonshot-ish in hindsight, some I found out somebody else already did without my prior knowledge (ie self-belaying device for climbing), some just look hard but doable.