In the past it was the norm to grow hair longer. The prophet and Imams did also have that however they maintained it clean and tidy. When they perform the hajj they would shave it all off as it is Wajib for first timers and highly recommended for pilgrims after the first time.
There are certain things that were performed in the past because they were socially acceptable for men. Today they may give off a different impression. For example the long hair or the eye kohl which men used to practice. Today this may be regarded as imitating women. If that is the case then it becomes haraam and unacceptable. If the intention is purely to follow the Sunna of the prophet and there is no attempt to look like or imitate individuals whose values are against Islam then it is okay.