Because it is a job. It takes a lot of work and dedication to effectively hold an office. I don't know if I would expect Every officer to be paid (simply because I haven't given it much thought), but someone like a Secretary should definitely get paid. They have to be on call to answer questions, both in person, by phone, FAX and email. Many times they head up different committees, converse with other Lodges and Grand Lodges. They are the go-to man for many things. Their attendance is more important than probably any other officer in the Lodge. Then I start thinking "Well is it fair to pay a secretary and not the WM that he works for?" And I'm just speaking at the Lodge level. If you get into the Grand Lodge level there's even more involved and the pay should be increased.
Another post mentioned having expenses paid rather than being paid. But I feel it isn't so much about the expense, but rather the time and effort put into it. Since someone also mentioned traveling I will use that as an example: When someone asks for a ride from someone and the person giving the ride asks for gas money, it wouldn't be out of the ordinary for the person to ask for $10 or so. Since they are only driving 10 miles and the average car gets 20 miles to the gallon should the person only ask for $0.90 (half of the price of 1 gallon of gas)? No, that $10 or so isn't for the gas, it's for the inconvenience, the time spent doing something, the wear and tear on the vehicle, etc.