I don't. Most of the music I've played in an orchestral setting hasn't really been that loud; there are certain sections of a piece where you might play louder than usual, but most is fairly low in volume. Wearing earplugs would mute everything else, including details you might need to hear, feedback from the conductor etc during rehersals etc.
As an (amateur) percussionist/drummer I will typically only using custom earplugs if I play a really piercing instrument for extended periods, such as bells, chimes orchestral cymbals, or if I'm standing close to them.
A drum kit in an orchestral setting is usually not that loud, at least not from my experience. Drum kits in band settings on the other hand... In those settings I'll usually wear in-ears whenever possible, which gives me a mix of whatever I need to hear, as well as a little bit of my drums so that I can hear what happens onstage. If not possible, I'll wear custom plugs which reduces everything more or less evenly with ̃~25dB.