There are a lot of good reasons for playing in an ensemble or orchestra, but I wanted to highlight just a few here.
Not feeling so exposed. I started private lessons when I was 10-years-old. As a beginner and a kid, recitals terrified me to no end. I got over that eventually by doing it more and survived the ordeal. Playing with the orchestra was an entirely different animal, and I loved it. It really helped me with my stage fright, because I wasn't the main focus, but I was still making music. Not only was I making music, I loved the glorious (if not always perfect) sounds coming from the other sections and how it all melded into something more than just one thin cello part.
College-bound? Set yourself apart from the crowd! Securing spots for colleges and scholarships are more competitive than ever. My daughter will be going off to college soon and has done a lot of research on how to set herself apart from other applicants. Obviously the strength of curriculum and test scores and GPA is paramount, but what they also consider important is, and I quote: "Extracurricular commitment. What counts most to colleges is how long and how deeply you have been committed to one or two interests, how much time you allot to them, what leadership roles you have undertaken, and what you have accomplished." If you have a passion for music and your instrument, why not make it work to your advantage? Leadership roles within a ensemble are a very real thing, as section leaders are responsible for keeping their sections together, and running sectionals.
It will benefit your future career. Teamwork, good organizational skills, effective time management, coping well under pressure, and discipline all play a part in an orchestra/ensemble. These are the qualities that employers look for in a prospective hire. Having worked in corporate America for decades, I can attest to this. Ask anyone with a job!
It keeps you sane. Making music is incredibly therapeutic. No matter what else is going on in your personal life, that all goes out the window once you start playing. Your concentration shifts to your music, attention to detail, and everything else melts away. Your brain is tuned in (no pun intended) to the music and getting a huge workout that TV can't compete with.
Personal satisfaction from making a difference in the world and filling the air with something beautiful. Self-explanatory.
"We are the music makers, and we are the dreamers of dreams..."