This is a question you have to ask yourself at the outset of your studies, as it underpins the motivation you have to pour countless hours into what is undoubtedly a difficult hobby. It's very easy to burn out if your reasons don't provide you with the adequate drive to overcome the many hurdles and embarrassments you will face. Nobody can answer this question for you, but your reason(s) probably falls into one of several broad categories:
Intrinsic love of your Target Language(TL) is the greatest and possibly least common motivator for language learners. If your motivation does happen to fall into this camp, I have one piece of advice: Do not let anyone convince you that your TL is pointless. Do not be convinced to study a different 'easier' or 'more useful' language instead. If you are genuinely interested in pursuing your TL for its own sake, you are in the possession of a lifetime passion; that's worth a lot.
I remember scoffing at this reason when I was younger, even though my passion for Japanese unambiguously originates from my love of anime and games, but it's not a terrible reason honestly. If your goal is to learn a language anyways, integrating it into your other hobbies is surprisingly efficient. Regardless of which language you choose, consuming media in its native language can help speed up the learning process and provide you with a deeper understanding of the works in question.
Studying a language for the benefit of others is definitely a good reason, but I don't necessarily consider it a personally compelling one, especially when the people you are studying for aren't interested in meeting you half-way; you may even find yourself somewhat bitter towards the people you're putting in the effort for. Still, if you live in an ethnic enclave, it genuinely hurts to not be able to talk to the people around you, so it's an understandable pursuit.
Studying to advance your career is simultaneously a really good reason and a really bad motivator. I think it's probably a lot easier to justify if you're still in school/college, but when you're cramming language study into your busy weekly schedule, it's a lot easier to do it if you actually want to and not because you think you need to. If your goal is to work abroad so you can afford to travel to your TL's native land, I can see that, but I would recommend traveling to the country beforehand before you sell your house.
Do not learn a language to impress others, you absolute mongrel. Even if you mananage to become fluent -and you won't- the clout you receive from doing so is hiliariously short lived. Most people will be impressed that you're bilingual for all of 20 seconds before they forget all about it. This journey is not about a title, as the title isn't even worth having in isolation. It won't get you laid and it won't make you new friends UNLESS you are genuinely impressing the people who speak your TL natively, but again, you're not getting there with that motivation alone.
In 2022 I worked on a translation project for an extremely girly Korean children's show. Season 1 had a full on dub, but season 2 hadn't been translated and while I don't currently speak Korean to any meaningful extent, I managed to stumble on JP fansubs from Nico Nico Douga. Before I knew it, I started translating and republishing the episodes via Twitter. Unfortunately the fansubs in question were missing the last 8 episodes; by the time I realized it, I had already translated about 8 episodes myself. It's been a couple of years since the time of this writing and I still find myself dabbling in Korean in the vain hope that I can someday finish my work. I defy you to find a sillier and less effective reason for studying a language, you won't.
For better or worse, I have subjected myself to every single one of these reasons at some point when attempting to study a language; as you can see, some reasons are better than others.