Almost as soon as the first general purpose computers were developed commercially in the years following World War II, demand for their number-crunching power far outstripped availibility.
Because the cost of building computers was so inherently high, it was more economical to build computers as large and powerful as possible. In order to justify the considerable expense of a computer, businesses, universities and government agencies had to make as much use of them as possible. In many cases, this meant running them 24 hours a day and, often, renting out time not needed by the organization's own staff.
Gaining time on a computer was thus expensive and often hard to obtain. In such an environment, it's no wonder that computer designers and theorists dreamed of a computer small and affordable enough for everyone to have access to their own.