You don’t know what you’ve got until you lose it!
Freedom of movement was a two-way thing, not one-way as generally portrayed in the media
British citizens had the right to live and work in other EU countries, crossing borders at will, without time limits.
Musicians could travel around easily without worrying about borders.
Business people could pop over the channel for meetings without difficulty, and travel between EU countries.
Lorries could deliver their loads across the channel and then pick up a return load in any other EU country before returning across the channel.
See Losing freedom of movement: pain but no gain for far more detail.