Monero (XMR) is perhaps the most desirable privacy coin, since it fully anonymizes the origin, destination, and amount of a transaction. These anonymity features are mandatory on the Monero (XMR) network, unlike Zcash (ZEC) which is optionally transparent.
Although the anonymity features of Monero (XMR) may be good for users who want to maintain privacy, regulators consider this anonymity to be dangerous, since there is no way to know if Monero (XMR) is being used for money laundering or other illegal activity. Likewise, exchanges which offer Monero (XMR) are taking the risk that they are facilitating illegal activity, which is in violation of the anti-money laundering (AML) protocols required to be officially licensed.
An international council of regulators called the FATF has actually mandated that cryptocurrency exchanges worldwide ban privacy coins by 2020, and it seems most countries will enforce this rule.
Even Zcash (ZEC), which is optionally transparent in order to be more compliant with regulations, was banned on OKEx Korea and Upbit and may face bans worldwide. Other privacy coins under the gun include Dash, Horizen (ZEN), Super Bitcoin (SBTC), Haven (XHV), Zcoin (XZC), Grin, and Beam.
That being said, the anonymous nature of Monero (XMR) and other privacy coins makes it practically impossible for regulators to stop users from setting up blackmarkets where such coins can be bought and sold. Therefore, the intrinsic nature of privacy coins means they will be around long term no matter how harsh the regulatory environment gets.