Most people in telecom are old and are analog phone people, they don’t know ip/sip and don’t want to learn.
It’s basically a small networking job that you never get calls on nights and weekends about and if you do it’s a system you can reboot remotely. If it’s not the system it’s a switch and its someone else’s job.
Telecom isn’t sexy but it’s still needed, no one’s going into it as it’s not ‘sexy’ and to be honest it’s easy AF.