In fact, most of Jewish life centers around adult life. It doesn't make much sense to finish preparation for adult life at age 13. There's so much more you should learn about Judaism than can be taught by age 13, you should continue your Jewish education. Synagogue attendance enhances your Jewish education and makes you a participating member of your Jewish community. In an ideal world, this wouldn't be necessary, but we all know that some people need a bit of pressure to meet expectations.
Custom plays an important role in Jewish life.
These are customs that have been part of Temple Beth El for a long time. Although some of these examples may seem years away for you, the point is that teaching is part of what a Jewish adult does. At a Shabbat service, we are concerned with teaching Torah. Presumably, you have studied your portion, and you can teach a little about it. Many of the people at the Services can't read or understand Hebrew.