My Daily mixes are not playing certain artists

[Eketo]

Plan

Premium

Country

Device

Android phone and laptop

Operating System

Android Oreo, Windows 10

My Question or Issue

For the whole time the Daily mixes have existed, they've seemed to leave out certain artists, at least for me. Most notable in my case is London Grammar, which has been my most played artist/band for three years in a row now, yet the only song by them ever to appear on any of my Daily mixes was a song they made with Disclosure, so basically it wasn't them on the playlist, but a song by Disclosure in which London Grammar was featuring in.

Is there an explanation why some artists never appear on the Daily mixes? London Grammar isn't the only artist that I have this problem with, but as I said, since it's been my most listened artist/band for a while now, it is very strange that their songs are never on the Daily mixes.

On the other hand, some artists that I never listen to seem to appear on each of the list after just one listening. Like for example my friend played a song by Beyonce on my account, I never listen to Beyonce nor do I particularly care for her music, but after that one song being played Beyonce appeared on three of my Daily mix playlists the very next day.

So how exactly does the Daily mix algorithm work? Is it more favorable towards some artists based on their general popularity and is there a reason it seems to be leaving certain artists completely out, even though they are being regurarly listened to?