Why?

At the most you need to use an external service for delivery (usually because you have problems with MS) but you can still run your own server with no difficulties once you do that.

That said, DMARC is required by a lot of people now, so I do not think this particular issue is a problem.

I have been self hosting my my personal email (and for family). Few problems so far other than delivery to MS and I have recently moved a domain I use for work email over.

Oddly enough the MS problems come from hotmail, but not other services. If that is a problem, then pay a bit to have email delivered.

It's not enough. I have a domain that I had a very long time but it is on an undesirable tld. I got it long before it was problematic. Outlook always puts my mail in the SPAM folder even though I have done everything I could. I even deliver through a trusted provider. Not on any spam list. DMARC, DKIM, SPF all set up. No dice.

I've never had a problem not having dmarc. DMARC doesn't really mean anything. The security comes from DKIM (or SPF, but that's garbage)