Why do some married women look outside Marriage?

I've noticed that some married women talk to other men online or in person, even when they know it could hurt their marriage or put it at risk.

Do you think it's mainly about physical attraction and lust, or are there usually deeper reasons behind it? Things like feeling lonely, not getting enough attention, wanting excitement, feeling emotionally disconnected, or missing something in the relationship?

For women who have been in this situation, Is talking online different from meeting someone in person, or does it come from the same feelings?