Not knowing Tufts' specific situation, the answer to the question "why doesn't (insert school) play hockey?" is almost always money and that they can meet the requirement for equal opportunity through cheaper sports.
Hockey is not a cheap sport to play. Facilities cost money, especially if you're renting ice time. Even if they own the rink it costs money to keep up the ice (energy for cooling, Zamboni, etc). There's a lot of expensive equipment to buy (sticks, skates, pads, helmets, pucks, skate sharpener, etc). Compare the cost of equipment and facilities a team needs for hockey compared to soccer, basketball, volleyball. Also, hockey players can have a higher rate of injury with bodies flying around the ice.
Opponents are further apart since there are less teams so there's more travel involved.
If a school finds they're able to meet equitable opportunity with cheaper sports, they may choose that route over hockey if they don't feel it's a particular priority of the campus community.