It is because we have been selected for a much longer lifespan than mice. Basically during human evolution there has been a selection process for greater resist

It is because we have been selected for a much longer lifespan than mice. Basically during human evolution there has been a selection process for greater resistance to developing cancer - if we got cancer at the rate mice get it almost nobody would make it to be a teenager. Humans are by animal standards very long lived and naturally quite resistant to developing cancer. We have many more anti-cancer biochemical and genetic systems (antioncogenes) that work much better than the same systems in mice.