Ok maybe not everything, but being able to transcribe things will improve various important aspects of your playing.
Firstly, it takes the pressure off remembering things. Before I was in the habit of transcribing, I would spend hours working out a song or lick or solo, only to find that I couldn't remember it when I revisited it sometime later. It's much easier to re-learn than to learn from scratch, but still, it was frustrating to have to work things out again. Now that I've got things written down, that problem has gone away.
Secondly, it forces us guitar players to understand rhythm notation properly. Tab is an extremely useful system, and beautifully clear in terms of pitch; the lines are the strings, the numbers are the frets, excellent. However, all too often the rhythm is overlooked. If you ever come across tab without any rhythm notation, discard it. Half the information is missing. Arguably the more important bit. Don't get me started on “”””Lead sheets”””” that are just lyrics with chords above the words. To get music, rather than just pitch, off the page (or screen), we absolutely need to be able to read the rhythms. Being able to transcribe rhythms therefore massively improves our ability to read them.
Rhythm notation can seem intimidating at first, but for the vast majority of things you'll ever encounter, you need to know only a dozen or so symbols and a few basic rules. As with learning any new skill, start small and simple and slow. Look at transcriptions of melodies you're familiar with, and see how each symbol relates to the note length. A good teacher will be able to take you through these fundamentals in a single session, so I'd encourage you to ask about it in your next lesson.
Finally, you know how there are some things we play that we kind of just fudge/blag? Sometimes that's totally fine and can bring interesting results, but often it's something in our playing that we dislike. Transcribing that thing will make us decide exactly how it should go. If it's a lick of our own, we get to make that definitive decision, and if we're transcribing someone else's music, we must slow down the recording and work out exactly what is going on. No more fudge, this is how it's played. Even if that isn't, in fact, exactly how it's played, you'll now be playing it the same way every time, and it's become part of your vocabulary.
In terms of tools for transcription, we have some options. We can go old school and use pen and paper. Nothing at all wrong with that. Personally, I use notation software, for a few reasons. Mainly, I don't want lots of paper to sift through, but also being able to hear the playback of what I've written will instantly highlight any mistakes I've made.
I recommend Tux Guitar to my students as it's free and does a decent job at the basics. MuseScore is a fantastic free notation software that is capable of notating any instrument and also includes the ability to write in Tab. As it's not guitar-specific, it lacks (as far as I know) the ability to notate some articulations you might need. The best software I've encountered for this purpose is Guitar Pro. This one isn't free, but it does an excellent job at what it sets out to do. The interface is clear and intuitive to use, and all the articulations and symbols you could want are available.
So, if you haven't spent much time writing down things you've come up with or learned, I'd encourage you to give it a go. You'll find that it really does improve your playing!