A new job role takes generations to be standardized. PM as a standalone position in tech companies didn’t exist anywhere until the late 1980s, and dedicated PMs didn’t become commonplace at most tech companies until the last decade or two. Even today there are many tech companies (especially outside traditional tech hotspots like Silicon Valley and NYC) that don’t have dedicated PMs.

PM job functions have always existed—after all, someone needs to define what features go in the product! But pulling those responsibilities out of Marketing or Engineering into a dedicated role is very new by business-history standards. Especially compared to disciplines like Sales or Marketing or Finance that have existed in very close to their present form for over a century.

Because the PM role is new:

• There’s not yet a clear university education/training path for PMs. Whenever you get self-trained people entering a job role, you’re going to get more variation than if there’s a standardized university curriculum driving uniformity inside a job role and differentiation between related roles (e.g. architects vs. structural engineers, or doctors vs. dentists).
• New things generally evolve faster than older ones. This is generally true in biology, in product design, in human relationships, and even in job roles. Over time, less-successful variations are weeded out and the winners at early inflection points tend to define standards for the next generations.
• Many tech company CEOs and HR managers don’t know what to look for in PMs. This includes both older CEOs who came of age in companies that lacked a PM function, as well as young founders out of university who never worked with a PM at school. The result: when it comes time to build a PM function, they’re not sure who to hire and what to ask those hires to do. This unfamiliarity drives diversity.

In addition to PM being a relatively new specialization, dedicated PMs aren’t needed during the early stages of a new company when the product is simple enough that someone can manage its priorities and evolution as a part-time job while also doing other things, like being the CEO. This means that when the first PMs are hired into a company, the PM role needs to squeeze into areas of responsibility that other people are already doing. Depending on the competence, enthusiasm, and political savvy of those existing “part-time PMs”, the resulting PM role might vary. For example, a small company with a very good designer as part of the founding team might not include UX design as part of the PM role, while another company might include design in PM wheelhouse.

Finally, *everyone* has an opinion about what features should go into the products, and when. As a result there’s often more jostling over the job scope of a PM that you don’t see in roles like accounting or QA that tend to evoke fewer passions.