As a general rule, no, linemen do not need to weld. However, it depends on what you want to do with your career. If all you want to do is poles and wires then forget about it. But if you want to get into other areas such as substation construction then it is a very useful skill. Company I used to work for decided to start building their substations in house. I volunteered and became certified in MIG and TIG for steel and aluminum and built up what seemed like miles of buswork. Was always challenging and interesting figuring out the angles and how to hold everything together while you welded it up. Not something I would have wanted to do every day for the rest of my working life but made a nice change of pace. And as Clive said, its a great skill to have for personal use.