Why is Zcash not really a privacy coin?
Because most exchanges I know only accept depositing and withdrawing coins to and from transparent Zcash t-addresses... there is nothing private about that.
If privacy for Bitcoin would be optional I suspect that not many exchanges would enable private deposits/withdrawals, but it certainly have much better chances than for ztrash.
Bitcoin is big enough for anyone to attack it directly, maybe that is why they started dealing with privacy stuff for ethereum and other shitcoins.
According to
CoinGecko, Monero is traded most on Binance - an exchange with 14 Billion US dollars in total trading volume over the last 24h.
I'm not an expert on centralized exchanges, but HitBTC with almost 2 Billion USD and Kraken with 500 Million US dollars total daily volume are also some pretty big names who list Monero. The latter I remember, recently introduced Lightning withdrawals; so it seems adding privacy to Bitcoin is certainly not something exchanges are completely shying away from.
Most reported trading volume on centralized exchanges is fake and washtrading, even on Binance, so I don't trust what they are saying.
On the other hand, one of the the biggest volume in Bisq exchange is for XMR and you can't fake that so easy, or you can't disable and halt withdrawals.