Value. Even though the 3070 is weaker than the 3070 Ti, it's more affordable. It's the same reason why there were more people with 1070 over the 1070 Ti, ironically, the same can't be said about the 2070 and 2070 Super due to the latter price matching the former.
EDIT:
The pricing is still very weird due to the sellers, if, say you were going after AMD cards then you might be fine, but with Nvidia, it's an mess. Then again, with people mostly going after Nvidia cards, sellers are going to charge high prices due to high demand.