Don’t see why DDG (a search engine) should run an email-service, nor vica-verse really.
That sounds like it violates the nature in which DDG wishes to brand itself. It seems DDG does not want to be the next centralized data platform (this kills their brand of privacy). The one product they already provide - search - is often times not better than Google results. They rather let you choose which search provider you want to use with their bangs system.
> as long as gmail dominates email and business email the privacy argument is largely irrelevant
I know Gsuite exists, but I have personally seen more instances of Office 365 than Gsuite for business in the wild. Not that Microsoft is any more privacy-friendly... just saying that I don't believe Google dominates business email.
There are already alternatives for every Google product, most of them objectively better.
The only thing keeping you locked into Google is you.
If DDG implemented their own set of apps, I wouldn't object -- but it wouldn't be anything that I'd actually use, either.