Besides the cost like another comment mentioned, the album is a dying format. Not to say it won't stick around to some extent , it's just not as popular as it once was.

Singles are the way of the present. Why?

It costs a fraction of the time and effort compared to a whole album
there is so much more competition for listener attention than ever before that putting out more than song dilutes the chance of a listener hearing the best work
the average listener isn't listening to whole albums, especially from a new artist they don't know of
getting onto a playlist is one of the bigger ways to get noticed, and no big playlists are adding anything other than single songs
for a band or artist that is actively trying to get noticed, there is a lot of effort that can go into advertising and marketing. Promoting one song, one music video for that song, one remix of that song etc. is a lot of work already and arguably more effective than promoting multiple songs. Think brand recognition.
they could be "saving" unreleased songs for a time when they are ready to release an album or EP, or they could be testing the waters to see if live crowds are into it before committing to a release or not
similar to some previous points, they may want to build a fanbase that will actually listen to an album, before just releasing it into the void

That's just my thoughts and opinion on the subject as hobbyist music maker, seeing what people are doing these days. I myself prefer albums and will listen all the way through, but it's no longer the standard.