There are also cultural differences.
There are lots of reasons not to judge other people or jump to conclusions about them based on behaviours you are used to/not used to.
Most of the time I actively think about having an appropriate amount of eye contact in conversations. But if we are talking about something that requires me to actually use my brain then I might not have spare cycles to devote to that, in which case I’ll decide based on the situation whether it’s more important to think things through or manage other people’s feelings.
Which means that when I am making eye contact with them it means I find our conversation trivial enough to not have to think about it and/or I am handling them with kid gloves. Turns out eye contact doesn’t always show respect!