The reason is that if you have a face that's round (is not rectangular) or is kind of wide, then bulking up will only make your face look more round or wide. It won't look more masculine, it will just look like you're overweight.
If your face is kind of round, then what you should do instead is cut or lose weight, this will hollow out your cheeks and give you more cheekbones.
It's also a common misconception that girls go out with muscular guys (like Stallone or Arnold). This only happens in movies. And notice in rare occasions where a guy looks good buff, is when the guy is really tall. This is because big muscles is in proportion to the height so it doesn't look weird. But if you're not really tall, being bulky actually will make you look shorter because of the proportion. Most girls I've talked to think that guys with big muscles is a turn off. They would rather go out with someone who is lean. Someone with a body like Bruce Lee, Usher, or Chuck Norris.
If your face is kind of round, then what you should do instead is cut or lose weight, this will hollow out your cheeks and give you more cheekbones.
It's also a common misconception that girls go out with muscular guys (like Stallone or Arnold). This only happens in movies. And notice in rare occasions where a guy looks good buff, is when the guy is really tall. This is because big muscles is in proportion to the height so it doesn't look weird. But if you're not really tall, being bulky actually will make you look shorter because of the proportion. Most girls I've talked to think that guys with big muscles is a turn off. They would rather go out with someone who is lean. Someone with a body like Bruce Lee, Usher, or Chuck Norris.