Why were glass houses originally built partly with brick and not all glass?

Some of the answers are partly right (ie to keep the wood frame off the floor) but the main answer is a cost issue. Glasshouses were first generally used by rich Victorian households about 160 yrs ago. At that time we had only just learned how to make glass in larger panes and it was very labour intensive and therefore an expensive commodity. So as well as keeping the wooden frame off the floor so it didn’t rot, and because they thought it looked better, they built the first bit out of stone or brick to keep the expense down.