Why doesn't riot like this happening? As I see it riot did not like mid taking wraiths so they buffed their health and did not buff the gold they give.

It's not that they didn't like it, they just didn't like how easy it was to do.

because junglers like gold too

If blue and wraiths belong to mid, red and small golem belongs to bot. What's left for jungle to take? A few crappy wolves?

They didn't like how easy it was for mid. To fix this, they buffed them and changed the location of the big guy. If you are mid, taking wraiths is still a good idea, but it takes more than 2 seconds for most mids now.