Because we are being limited by an artificial blocksize.
The amount of transactions in a block is related to the price of bitcoin, but on top of that the discussion about the blocksize and how to solve it also makes the users more scared to commit money into bitcoin and turns bitcoin fans towards altcoins even though they might prefer bitcoin.
Limiting blocksize limits adoption and growth, and therefore price.
on a related note, what happened to xthin?
Also those that hope segwit is our savior, some large mining pools oppose to segwit without a blocksize increase to accompany it. That is the true reason why segwit is 'delayed'