If you're a Mormon and you don't tithe, you lose your temple recommend.
If you lose your temple recommend, you lose not only your "forever family," but hope of reaching the celestial kingdom (highest degree) & you won't become a god of your own planet.
If you lose out on the celestial kingdom, Mormon theology is that you won't live forever with Heavenly Father.
So the tithe in Mormonism is linked to being "kicked out" of Heavenly Father's presence. Mormons say you can still live forever with Jesus, but not heavenly Father.
Hence, when Mormon leaders hold over your head...
...living forever with Heavenly Father...
...living forever w/your own family...
...becoming a god...
...well, hey...now you know why about 80% of Mormons tithe.
That's also sheer legalism.
There fixed for you. Since we know there are not more than 6 million that actually show up once in a while, the numbers from PR dept. are somewhat misleading.