I've never taken or destroyed a summit register, nor would I, but I've been atop enough peaks without cairns or registers to appreciate the absence of both.
I don't care who else has been there, how, or what his/her impressions were. I like the illusion, and the occasional reality, that no one else has stood there and seen the view and put in the work to get there.
Once, I climbed a peak in Glacier NP with two other SP members. One of them left a register. The other and I declined to sign it. Understand?
Years back, I signed registers because I thought it was cool to be part of the community. That was before I realized that hundreds or thousands might sign the same register in the same year. So I lost my interest.
I still sign registers for remote and/or difficult-to-attain peaks. For example, you'll see my name in the South Guardian Angel register.
But you won't find it in too many other spots nowadays. Most peaks I climb don't have registers. And most that do are time-killer peaks whose registers I'd be ashamed to sign for being grouped in with the frothing masses.