I agree. I think it's because they're stuck in the paradigm where the blockchain = the Internet. They think, "there is only one internet so there can be only one blockchain". With DPoS, blockchain technology becomes more analogous to a website. Anyone can create one but for it to have value, it must make a profit or offer some sort of novelty.
In my opinion it is because they are still stuck with the POW mentality. In proof of work, "there can be only one" (for a given hashing algorithm). A blockchain with low hash power is always at risk of a blockchain with much larger hash power using its excess hash power to take over over the small competitor temporarily just to cause some damage (double spends). Competition in free markets is great and all, but that's just sabotage.
In DPOS, on the other hand, taking over the network even momentarily requires letting go of real money to buy up the stake in the DAC. Buying up the underdog DAC just to kill it is a pointless effort, since that amounts to paying your competitors to just restart the DAC. This allows for true competition between DACs which leads to greater innovation in this space.