The fact of whether or not to use electrum in wallets is rather technical and resource-related. Although the ideal is to have your own node, which is highly recommended; but in practice not everyone is capable of doing it, knowledge and desire. Mobile devices are those that have been the traction for the use of servers like electrum, security is a little lower but mechanisms have been implemented to not fully reveal our public addresses to the electrum provider, as is the case with the BIT37 bloom filters, this has its security problems, and in 2018 with BIT157 and 158 implemented in wallets such as Wasabi, Blixt, Breez, LND, and LDK, the implementation of neutrino used for lightning implements this mechanism. If you want to delve deeper into the subject https://bitcoinmagazine.com/technical/why-bitcoin-wallets-need-block-filters