That's a great part of the experience when you're straight or curious or bi. You're accustomed, even pre-conditioned to having sex with women and being the one who takes the lead, while she gets penetrated.
Then when you have sex with a man, as the bottom, the tables are turned completely. You're submitting, you're vulnerable. You're giving a most private part of yourself for his use and enjoyment.
One past of being fucked, for me, was to gain some understanding and empathy for what it's like for the woman. When sex is agreed to, and is about to happen, when you're alone with a man and his hard cock, one thing is inevitable - he's going to penetrate you, and he's going to keep doing it until he's satisfied. There's a lot of connection and trust for that to work, for me, even in a casual hookup when I'm nervously excited, or with a fuck buddy who I know well and we know what makes each other tick.
There's a great sense of empathy and bonding with your fellow man, too. You feel vulnerable and submissive, but also it's empowering. He's fucking you, because you're able and willing to take it, and that's a wonderful thing. Especially, as is the subject of this thread, on your back with your legs up - you don't get any more submissive than opening your legs and offering your ass, with him in front of you and able to look into each other's eyes as he fucks you. Honestly you should try it.