Some might not realize it, but a lot of the 'new' sages are fueled by cultivation. There are some huge Sage farms that have been producing huge amounts of Sage.
Rosemary, Mugwart, Lavender, Cedar, etc. are all mass farm produced today.

By burning, do you mean smoldering so smoke appears or burning as in actual flames? Are the grasses in the smudge stick completely dried out and free of moisture? If they're still green, they probably will not work properly.

"Smoldering so smoke appears".........

The Smudge sticks are dry. If not, they will mold. Having moldy Sage is not a good idea to have around.

I use white sage leaves not a stick

Since I have trouble with smoke, I use crystals or sound for cleansing.