Fifty years ago, cellar cooling systems were predominantly refrigeration products with Prestcold and Searle having the industry sewn up, highly specified by the big breweries. This ubiquitous combination, being reliable products, had a large share of the market for many years.
However, in those days, it was quite a challenge to even quote for a cellar cooler, let alone have to install one. You first had to select the right size evaporator and then find a condensing unit to suit - they were not matched systems in those days! After deciding on the refrigerant, you then had to select the correct size expansion valve to suit the system, find the appropriate orifice and then a solenoid valve and coil, not forgetting a de-ice stat and thermostat. The condensing unit then would need to have an HP and LP switch fitted, as well as a sight glass, head pressure controller, an isolator and, last of all, a weatherproof housing for the condensing unit.
Then, of course, the system would need to be installed - with the extra time of having to fit all those components, you wouldn't get away with installing a system in a day like you would now. The process was a work of art for some but it wasn't cost effective and it was only a matter of time before the market would open out with the introduction of packaged cellar cooling systems. These new kids on the block had all the components already fitted and were off readily available from your local supplier.
Initially 'Packaged' systems were frowned upon by fridge engineers, as they were concerned that the air conditioning manufacturers were encroaching on the hallowed ground of the refrigeration industry, and besides, what's wrong with making a louvred housing of your finest timber to protect your beloved condensing unit - a hutch rabbits would be proud of!