Drawing in black and white is neither easier nor harder, but it 100% takes a different set of skills to depict things properly and to understand how to use contrast. People make the false assumption they can just take a colored page and turn the saturation to zero, then you end up with a blob of washed out greys or panels that are unparsable. You don't have to be as mindful with details when you can use color to bring to attention what you want! I think the biggest hurdle people face with trying black and white is learning techniques to inform details and objects rather than drawing everything outright.
I think if it's your personal choice, then people probably choose to work in color because that's what they're used to seeing or it's just what they want to see. Colors are naturally attractive, there's no denying that. I remember being a kid and picking up manga for the first time and going "but where da colors?" Same business!
I draw in black and white partially because i'm making manga, but also because I just don't care to use color. Black and white is easier for me to understand and I love it- over time I have only increased my expectations for art that just feels good to look at. There's something about just seeing linework with tone that feels very blunt, raw and "truthful", that is to say, you can't hide your shortcomings. I appreciate that.