Why are so many rest stops closed?

It seems to me that a way to increase rest areas and also save $$ is to create travel islands that service both sides of the interstate. They would have to be larger and better set up to accommodate the additional traffic. On the positive side there could be more of them servicing all while less of them per side. The money issue is real for most states and I do not see a major change no matter what political party. If we have a single rest area that services both sides we can lower our overall building costs as well as the cost to patrol and maintain them. We need to rethink how we do things to get the most of our State Dollars Special interest and entitlement eats away at every state budget.