Because we are deranged and very bored, and find ourselves amused by pictures of dudes with multiple appendages.
"Oh, but if penises -- uh, I mean hands --"
"Yeah, what's the use in having a big bunch of penises? It's not like you can chop them off and give them as a bouquet."
"I just imagine, like, four dicks coming at once. Gross!"
"I wonder if there are people who want penises as hands!"
"Oh my god, what a huge erection. Oh my god, it's like covering my screen."
"But boytaurs aren't REAL."
Not linking to the site in order to preserve everyone else's sanity. Google if you must.