Often people ask me "Why small, why not make bigger pieces?". There are several reasons both practical and creative.
The creative reasons take the lead for me. I have always liked little things, and details ever since I was a child playing with bugs in the garden or in the classroom with the doll house before school each morning. Many of my favourite artists create small/detailed art. So suppose I have a tendency to conceive of these things since it's what I enjoy. Secondly the found materials I regularly use dictate the scale of the piece in my mind. Proportion and scale are very important to my way of thinking.
The practical side is that thinking about petite projects and making them is easier when you're doing most of it at a desk the size of an A1 page, and other parts on a home workshop bench. However it's more of a happy coincidence than the studio environment actually dictating the scale.
Lastly, the reason many artists choose to work on a smaller scale - particularly painters - is that you can achieve a greater quality of finish over a smaller area, in a quicker time. This allows the artist a lower selling price based on hours put into the work, thus making the art more affordable to those who would like to own it.