Why are guys attracted to girls' boobs and butt?

It's an evolutionary trait, the breasts and buttox are fat stores, back in the days of apes and cavemen, a women was more likely to survive a pregnancy if she had extra fat to burn (because she would need it for te baby), eventually through evolution, man came to be attracted to a women with a large bust or bum because it would mean that it was more likely for her to survive a pregnancy, and that's why they are points of attraction today, however if you don't believe in evolution, I suggest you turn to the lies of your local church to tell you that you are sinning for being attracted to women

Guys instinct~

It's instinct.

Large butt = wide hips for child bearing

Boobs for breast feeding

basically, a good potential mate

Natural instinct, basically

Because its attractive. im bisexual though so thts not the only thing i find attractive. but thts not relative to my answer.

You could call it instincts

Men tend to be sexually attracted by the characteristics that make women different from them; e.g. breasts, shape of backside, smooth skin. This is a natural instinct installed in us by our Creator.

There is no need to postulate some evolutionary basis.