Transcribing, like many other things you practice, is a tool to be used to further your musicianship. There are a variety of uses depending on what you want to get out of it, and that's the key - always have a specific goal in mind. Don't just mindlessly transcribe a random solo then think "okay, now what?" That does you no good.
If you're trying to really get the style (articulation, inflections, dynamics, pocket, harmonic language, rhythms, etc.) of a particular music into your head, listening to and transcribing melodies and solos that are quintessential to that specific style will really help. It's like listening to a native speaker speak a foreign language that you're learning - you can hear exactly how to "say" certain things in the "correct" style.
If you're trying to get your ear training better (which is something I think many people need to work on more) transcribing will help with hearing rhythms, intervals, and harmonic progressions. Once you listen to and transcribe a bunch of different melodies/solos, you'll start to hear notes and rhythms in GROUPS rather than individual notes, and that helps immensely when creating your own music or trying to recreate someone else's.
If you're trying to increase your own improvisational vocabulary (harmonically, rhythmically, etc.) transcribe something THAT YOU LIKE!! This is often missed - people tend to transcribe what others deem "important" but often don't transcribe something they actually enjoy listening to or something they want to learn. If you like a way a certain player plays over the bridge of Cherokee, transcribe it! Then take that and put the changes over it. Now what part did you like? Was it the notes? The rhythms? The articulation? The phrasing? Figure out what specific part you liked, then see WHERE they played it, WHAT they played, and HOW they played it. Then you can take that and modify certain elements of it to incorporate into your own playing.
There are even more uses, but I think this is enough to get you started!
By the way - I often have students transcribe only the rhythms, or only the notes, or only the shapes of the phrases of a particular recording. Also you don't have to transcribe entire solos (I think I may have transcribed less than 5 full solos in my entire life) - you can just take the bits and pieces that you enjoy and want to dive deeper into. This is YOUR journey so make sure you get out of it what YOU want!