Because Bitcoin ETF will make better for Crypto ecosystem, Bitcoin ETF will make more high demand for Bitcoin itself and also others crypto. We can see price of Gold was increase all the times high after this asset approved by SEC to be apart of ETF. And Bitcoin will do the same thing if Bitcoin ETF to be approved.
I agree with the op more than with this. ETF is bad for ecosystem. Probably not as bad as bitcoin futures that blindly manipulate the price without caring much about the real one. The price could have increases if btc was approved, sure, but it would contribute to the general trend of trading cryptocurrencies instead of using them. People are starting to forget the initial ideas. Fiat has problems, cryptos solve them and give freedom. We should do our best to make sure crypto payments are accepted more and more. The obvious demand should appear and this will stimulate businesses to accept cryptos. As people are more concentrated on trading than on using, we are moving further from the main point.
But ETF could also be a bad thing for hodlers as well, because the price would've got hyped fast and big time by newbies once again, which would inevitable lead to another crash once some big countries start to regulate cryptos and set some limitations or something.