Because you do too many things together and you've allowed her to be comfortable with all these things, you became a friend and a roommate, instead of a lover. You're always there! Can't you see that, you guys do everything together, you're always there! You've never given her the gift of missing you, she knows where you are 24/7.
Go out, go to a different gym, start hanging out with your friends more, start going out on dates with other women. People take for granted the things they have and in doing so they don't appreciate them until they're gone, but you're always there!!!!
Have to chime in here as well. It's taken me twenty years to realize it, but that's EXACTLY right. We get into this place where we think spending time together will encourage closeness, which will in turn encourage passion, but it's all wrong, and I get it now.
She's BORED! You've got to do something to shake things up. Be bold! Do something she'd find shocking, and as robx says, DON'T include her. Make yourself interesting and a challenge again. She clearly likes you and trusts you, now make her WANT you. If I realized this five years ago, I'm sure I wouldn't be in the boat I am.
