There are plenty of straight couples on here. I'd even say more than Bi. What you seek depends on how you look. If you're new and impatient, then it may appear that way. I'd say simply take your time and find what works for you both. We've been here months and have yet to find something that strikes us as a match. There are tons of great people, so chat and see what's out there.
In almost all cases "bi" simply means there's more options on the table. We don't know anyone that requires no activity to play or have fun. Contact should be followed by a clear discussion of wants needs and no go boundaries. If a couple or single required bi or any other activity you don't want, then you simply say pass and move on from there.
When first searching on this site we certainly were not prepared for how many bi sexual profiles we would be looking at! We have come to appreciate all types in the community. We don't generally focus on whether the couple lists themselves as bi but rather whether they are looking for a straight couple and then take the conversation from there. You do have to dig a little deeper and have patience. Like everything else in this lifestyle communication is key.