For most shooters who own a .45-70 the attraction is multiple reasons. First being it's history as a US military cartridge starting in 1873. Then next being such a wonderful big game cartridge with a history of taking large game without destroying a lot of meat. And then there's the big, heavy bullet that's not affected as easily by crosswinds and holds it's trajectory quite well for long distance shooting.
The .45-70 is probably more popular these days than it's ever been in it's 150 year history!