Should all singers play or learn the piano?

I think everyone should learn.
I think that life is easier if you have a rootamentary understanding of something that can be complex or simplelistic.
It's like mathematics. The root of basic problem solving.

Yes I think it would be helpful

Anyone can sing but when you can play it on the piano, you can see it and visualize it as you sing. You can see the octaves and the notes and understand the difference between sharps and flats. Do much more

Piano's easy to learn, hard to get really good at.
I feel like anyone that's really invested in music should at least learn how playing piano works cause it's a good way to visualize or think about notes in your head.

When I think of a Fmaj7 or a am7 I usually think of the finger pattern on the piano first and I instantly know what notes are in that chord because of that.

If you're only interested in singing and not music composition or improv soloing, then it's not really necessary I guess

That's how Paul McCartney wrote all of his songs so it's probably not a bad idea.

Yes. synthesizer best instrument ever. musically speaking synthesizers are mans greatest invention. and a lot of piano music is beautiful.

[youtube=https://www.youtube.com/watch?v=ipjRmgi1WDw]

It definitely helps. I sing backup and because I played piano a bit, I find that it becomes easier to "hear" the missing note in my head. Being able to recognize intervals like 3rds or 5ths helps a ton.

Oh you mean it helps with the harmonies

If they want to