We have stucco as the siding on our house and there are NO dividing lines. Our stucco covered retaining wall have no dividing lines. Not sure what you are referring too?

Yes ... get a stucco contractor who will do a good job.

the house i'm in now is dryvit and i like it but it's not allowed where we are building. however, on the stucco homes, i'm seeing the lines. i asked my neighbor about this and he said they are expansion joints. do we have to have expansion joints?

You can read about it here.

http://www.cement.org/stucco/faq_spacing.asp

ok thanks. if i understood correctly, joints are needed every 18 feet. we won't have any stucco areas over 18 feet, so i don't think we will need them. i'll ask the builder in our next meeting just to be sure