No it’s not required, but it does make things a lot easier.
If you don’t you can setup a service like dyndns.com which allows for public dynamic DNS registration. Then setup a CNAME DNS entry on your public DNS for VPN.MyCompany.COM to point to the name that you setup for dyndns.com.
Then have your employees connect to VPN.MyCompany.COM.
Make sure that your TTL for the VPN.MyCompany.COM CNAME is setup for the same TTL that DynDNS.com uses.
Except when using VPN Routers. They require IP addresses thus you must have a static IP address to bridge offices using a VPN tunnel.