An interesting observation that has always fascinated me: it is only in software industry and drugs industry where we refer to customers as "Users". I don't know of any other.
For instance, we talk of "User Acceptance Testing" as opposed to "Customer Acceptance Testing" when referring to final software acceptance testing.
What are the origins of this?
It's an amusing point. As others have noted, in the computer industry the "customer" and the "user" are often not the same person, so we need different terms for them. Of course this is true of many other industries, too. But I think most other industries have more specific words. The person who buys a car is generally referred to as a "customer", but anyone who uses it is called a "driver". Likewise in the publishing industry someone who buys a book or magazine is a "customer", but someone who uses the book is a "reader". The appliance industry does talk about "appliance users". Maybe there are other cases.
Maybe the distinction is more pronounced in the computer business because customers and users are more distinct than in most industries. The customer is usually upper management; the users are usually clerical workers. Well, I suppose you could say the same about many products that are typically sold to businesses. Like, the person who buys a forklift truck probably isn't the person who drives it.
I think this is more an "additional musing" than an "answer". Whatever.
In the software industry, the customer and user are not always the same individual. The Customer is the one that pays for the project (such as the Finance department), the User is the one that uses the proudct produced as a result of the project (such as clerks in an office). Usually, both parties should have input to the process of creating the product.
I can't speak for the drug industry.
The OED’s earliest citation in a drug context is dated 1923, and 1950 in a computer context. The description users is understandable in both cases. Those who use computers are not invariably customers, and drug addicts are not customers as normally understood.
I’m not sure it’s the case that users is found only in the software and drugs industries. It might also apply to those who receive other services.
Maybe the reason is logic?
Customer is defined (WordNet) as
someone who pays for goods or services
where
User is defined as
a person who makes use of a thing; someone who uses or employs something
As both with software and drugs it does not matter who bought it, but who actually uses it, to me it sounds logical.
"User" was first regularly associated with the concept of narcotics starting in the first half of the 20th century. By the 1950s in the US, "drug user" became a legal term with a specific definition.
In sources prior to that (or at least those visible in Google Books), "users" tends to refer to either users of public roads or, earlier on, users of property. As "utilize" would be an appropriate verb to describe these people's engagement with roads/property, this usage seems straightforward.
My hunch is that the word "user" was a convenient, sanitized noun that would cover any drug and any manner of attaining a high. Separate legal categories of "drug injectors" and "drug inhalers", etc., would have been needlessly complicated and, from a legal point of view, an unnecessary distinction.
Software is similarly utilized in many different ways. The term "user" enables us to refer to one group of consumers, rather than having to group users based on what type of software they use or how they use it.
I worked for a bank, back in 2002, in Brazil, and in Portuguese, we have the same problem. We changed a little our vocabulary because:
User: is more for a drug user, than a customer
Attacker: is more a football offensive player, than an aggressor
Antivirus: the only analogy that you can make is a vaccine. In the "real world" there is no antivirus, just vaccine.
customerimplies a person who is paying.. I don't think it would apply to software development as a LOT of things are done for freecustomeris not theuser, though thereuseris usually replaced byconsumer.