Hello everyone! 
Thanks so much for this feedback. We’re constantly improving custom network support. Unfortunately, this request has been rejected.
MetaMask aims to be the most extensible and decentralized wallet, enabling permissionless access to the whole decentralized web while protecting the privacy and security of the community.
When users hit 3rd party RPC endpoints, their account list is visible to the host of the 3rd party RPC endpoint. This would allow 3rd parties to collect balance information on MetaMask customers, and is not something we can allow by default. Instead, we’ve opted to allow the customers of these networks to opt-in specifically to the networks they wish to.
Our approach to user experience is to enable users to opt-in to the things they want, without forcing additional features on those who don’t need or want them. The more third-party end-points we query, the more the performance of the wallet is affected. This is especially important in emerging markets where millions of people are onboarding into MetaMask to find freedom from legacy internet and financial structures.
We will continue to improve the way the wallet works on these custom networks, while also maintaining a strong culture of decentralization and consensual interactions. We recently launched a Custom Network API that allows developers to easily suggest networks to users, with this goal.