My piano is not played much. Does it still need to be tuned?

Yes. Playing the piano (or not playing it) usually has very little effect on how long the tuning lasts. A typical piano string is

pulled to approximately 150 pounds of tension when it is at the correct pitch. A string under that much tension is going to stretch. This stretching, along with other factors, causes the piano to go out of tune even if it is never played. So periodic tunings are needed to compensate for this stretching.