I was thinking to add dig spots to hoenn. Reason - No one goes hoenn after completing once there are some quests to go like excavation but many people don't do it. Dogs are common thing to do for all cuz we can do it after 1-2 badges. If we add dig spots to hoenn people will go there to dig in order to make money.

I'd say +1 but Hoenn has excavations. I'd instead incentivise excavations more rather than adding more dig spots.

But all don't have access to excavation. Dig spots are common and all aware of it.

I don't think that devs will add new dig spots to Hoenn. We already got the excavation sites, which is way more profitable than doing dig spots every third day. If you do them frequently, there is a good chance you will get a good Pokemon, which you can sell for a good amount of money. For the people who aren't aware of this, there are guides on the forum & they can always ask it in the Discord server.