Is your question "Why
shouldn't tapers be used on a daily basis" rather than "Why
should tapers be used on a daily basis?"
Because using tapers on a daily basis is not a good thing. They are meant to taper the lobes once, and then taken out to be replaced by plugs as soon as the fistulas are stretched.
But addressing your main question, you might want to consider stretching through a different method. Maybe you can try taping, or I know some people will stretch with glass/steel spirals over a number of days. It just depends on what you want to do, and more importantly, what your lobes respond best to.
And just remember to take your time with stretching. Yeah, I really look forward to getting to my goal size; I plan out how long it could take me, but honestly, it's up to my ears how long it's going to take. I just have to pay attention to their limits and know when I'm pushing them. If I push too hard, I could injure my lobes.
I suggest that you wait a bit longer. Give it a couple of more months before trying again; maybe they're just not ready to stretch yet. In the meantime, keep massaging and take of those lobes good! ♥