Comets are large so you need a low magnification. Big telescopes can only work at high magnification - and also, cheap amateur telescopes are designed only for high magnification, because most people just look at the Moon and Saturn and that's about it. Binoculars usually have reasonable low magnification, like 8x to 12x. (Don't buy zoom binoculars that go up to very high magnification like 30x, those are trash.)

Comets are also dim and diffuse, and we can see dim objects much better if we use 2 eyes rather than just 1.