Because it has huge supply.
If a coin has so much suplly it cant make easily 1 Dollar you know?
There's a clue already in the market by just looking at the coinmarketcap. Although there are some few coins that have reached $1 despite having billions in supply and that was XRP.
But compared to the total supply of Shiba Inu, it got trillions in tokens printed and that's really too much which makes it very unlikely to reach $1.