Because Apple engineers are disconnected from what real people do on a daily basis. Not only did they remove telnet, they also removed ftp — ostensibly due to security concerns. Although sftp remains, some sites do not support it.
And, drumroll, Apple tampered with the /etc/paths file so that /usr/local/bin now is the first element of $PATH, and not the last as it has been for years. Be careful if you have same-named commands in /usr/local/bin, as in other macOS binary locations, as the results may be different than you expected.
I edited the /etc/paths file to restore the proper search path element order. No need for more surprises.