ir, Torah (learning AND living) and tznius is what helps us in our struggles against the y”h, so consequently this is part of what helped us adhere to Torah living. But it’s a cycle. Learning for the sake of learning about our traditions without doing the mitzvohs of keeping Shabbos, bris milah, eating kosher, etc. will not get us too far. Therefore chumros help us to ADHERE to halacha and to practice and live with halacha.
Remember, part of what the Chashmonuim fought the Greeks was because of Shabbos and bris milah too.
Chumros is not the right word, it’s true. But I am talking here to people who see it as such, much like I see some very frum people practicing what I feel is chumros that the Torah doesn’t demand of us.
But the truth is, whatever keeps us from violating halacha is part of halacha and they are not chumros.