Why YAHOO has got lots of SPAM While other email providers dont?

My Yahoo Mail always receive Spam emails while Gmail,hotmail does'nt even 1 why? I mean Everytime I open emails they will be 20 new emails and in those 20 ,10 is SPAM. If I go to my google If i open I fine 10 emails sure they meant for me, on YAHOO you find people telling you about products,LOTTO, ENLARGMENTS, how to make money.I mean I dont have to purchase an email for protections like this YAHOO MUST INCREASE SECURITY when it comes to something like this