Depends. If they are devoting all their time to their cell, then I might be. However, if they are just playing on it a little, then no. I spend a lot of time on my phone. My accounts online are set up on my phone. I talk to students, my family, and fellow bloggers. I'm a busy lady and all of it can be done from my phone. So, my face is often buried in my phone.
Have you ever asked what your SO is doing on the phone all the time? Are they playing games, chatting, or what? I would recommend talking to your partner. Communication about everything is important. It might help you understand why they are on the phone. Plus, maybe they don't realize you want attention at that moment.