I would say no - if the betta doesn't attempt to build a bubble nest, then don't worry about it. He would certainly build one if he wanted to. A sick betta will probably not attempt a nest, but barring that circumstance, it's ok if they don't. I have had many bettas and some were prolific nest builders and some weren't. Of my current two bettas, one builds large nests fairly frequently and one never has built a nest. My bettas are in 10 gallon planted tanks so the water parameters are excellent, and the bettas are healthy; in fact, they are the longest-lived bettas I've ever had.
I have read that younger bettas build nests more frequently than older bettas. My one betta that builds nests is almost two years old.
Some of the reasons that Heidi mentioned above should entice bettas to build a nest: when the betta is content and healthy, when they are ready to mate (although my male bettas never saw a female), when the water parameters are good - I have read that bettas will make a nest when the water parameters can support fry.
I'm sure that my one betta is happy and healthy, although he never attempted a nest. In that case, if everything else in the tank is good - water at the proper temperature and clean, etc. - then I wouldn't worry about it. If Sammie is healthy and happy, maybe the nest will come in time. If not, although you'd like to see a nest, I'm sure, I don't believe it's anything to worry about.