Not on a lot of leases, and on the ones where you can, there tends to be fees and a pile of paperwork. Yes, sufficient foresight would have seen the possibility that needs might change, but foresight is in surprisingly short supply in general. For those who can sublet, as I said, corporate inertia is hard to overcome. The businesses that thrive will be the ones who find a solution that works for both the business and the employees.