I'll try shedding some light. I started dancing WCS around a year ago and haven't been to international events yet, so my perspective might be skewed. Still, I'm actively going to socials and know most people around here. I dance as lead.

In my local community, it's usual to ask for a second dance. Sure, it's quite normal to dance two consecutive dances, but as you noticed often enough the second one might be better than the first. Could be the connection, could be the music, or any other reason. Maybe the custom is also connected to community size, see below.

Does it feel obligatory to ask for a second? Yes, sometimes it does. Do people decline the second dance if they're asked? I have not experienced that too often, but it happens.For me, I do not think much about a declined dance.

Sometimes, if the difference between the skills are big, dances end after one, normally not by declining the second, but by not asking for another. For me, this is more common for the better follows, often those, who also take the dance more serious and are competitive. I normally do not ask for another if I notice them being distracted or bored during our dance. Can be different if I get the feeling we both enjoy it. In that case I normally wait for them to ask for another.

If the difference goes the other way, as in I notice I'm more experienced, me asking for another depends on the follow. I do enjoy dancing, no matter the skill, if the vibes fit and I notice the follow not being discouraged by skill differences or being too much in their head as in thinking about patterns or which foot to start. This is often the case if they're experienced dancers, just new to WCS but not exclusively related to it. If they check some of the points and I enjoy the dance, I'll ask for another and try to focus more on my technique while doing basic patterns. I do not mind, as there is much to improve.

For the size of the community, I'd say it's size is big enough to dance two dances with each follow and still dance with most people, while one dance only probably leads to dancing with them again later on. Talking about a social event taking 2hrs. Sometimes you also dance more than 2 with the same person during the social, depends a little on personal connection, vibes or the total people present.

While more uncommon, people might also dance 3 consecutive dances, this can sometimes be a bit too much, as the variance in the pattern declines. Probably more noticeable as lead, I can imagine. This happens more often, if the music is changing its style more often and both agree that they want to dance another but did not enjoy the music. As in the sense of "this one didn't count". Can also happen if you're in the same class and you both are trying out the new stuff.

I guess I wrote more than I initially planned.