the issue exists independently of who loves or hates mouse.

When the Concord Line (Yellow) first opened,there was a candy bar vending machine inside fare control at either Walnut Creek or Pleasant Hill. Later,BART leased kiosks to a chain which sold paperbacks, BART high value tix,and COOKIES at Civic, Powell, & Montgomery. BART insisted they stop selling cookies so they closed. Now we have both physical food/coffee outlets within the stations. NONE of us want the level of half eaten food which sustains the rats in the New York Subway. That said, busting a rider for eating is so much less important IMHO than keeping the stations and trains both clean (bring back the trash cans) and free of nodding off junkies.
Any police force has either an official or unwritten hierarchy of which infractions to concentrate on. Fare beating is much more important to those who DO pay their fares, but we know busting someone for eating fills the ticket book quota and is easier.