Bias.
I interviewed at over 25 places through the past year. Here are my observations:
More than half the time the employer knew the work that needed to be performed in the near immediate but had absolutely no idea what they wanted in a developer.
Nobody can define senior. At some places they were expecting a senior developer who could do anything. At other places it was a trend chaser who plays with dozens of tools. At other places it was a framework user placing text on a screen.
Algorithms are where interviewers go when they don’t really want to talk to people. This is a danger zone because the candidate can fail any number of reason, most especially code style and vanity. Worse, many of these algorithms are completely outside of any real world concern better solved with a well formed data structure.
Unfounded assumptions are the standard. Most people writing software professionally have never done anything else professionally, which is a tragic silo. When you’re a hammer everything is a nail tunnel vision mentality is the expectation. In this case the goal, if want to be hired, is to fall into the middle of the bell curve. Don’t be awesome.