Why didn't they call you? There are so many reasons:
- the person in charge has something way more important to do this week and isn't making decisions or calling anybody - for example is on vacation, is out sick, is dealing with an urgent customer problem, or the like. Hiring managers often have to squeeze the work in among their regular duties.
- the process isn't over yet. For example you might be second choice, and they're waiting to see if first choice says yes or no. If first choice says no they'll reach out to you. In the meantime they don't want to say anything positive or negative to you
- they decided to hire somebody else and are too rude to even tell you so
Now, consider what will happen if you call. If they are just too busy with something else, they are too busy to take your call. If you manage to get through, you may have annoyed them. (I've said this before and I'll say it again, you don't need to worry about showing enthusiasm. You came in for an interview. You emailed. They know you want the job.) If they haven't decided yet, you calling won't speed that up and they have nothing to tell you yet. If they really don't want to hire you (the imaginary bad reference), to the extent they won't even email and tell you so, why will they be more helpful on the phone? If I thought someone would be a terrible hire I would never tell them so if they asked. There is no good side to doing that.
The only case in which this can help you is if the hiring manager is an overworked forgetful person who you happen to catch on the phone and who tells you "we're still working on it" or "sorry, we hired someone else." You should not be waiting for this information. If you're happily employed, continue working and think no more of this until you hear from them. If you're looking for a job, keep looking. You can't make this go faster.
Now, one exception. If you have new information such as "I have an offer from someone else but would rather work for you" or "I completed that course I told you I was taking; here is the certificate" then go ahead and provide that information to them. But don't just ask them what is happening. If they were willing and able to tell you what is happening, they would do so.