SaaS admin dashboard, mobile-optimization necessary?

Any of your SaaS products, particularly those with dashboards, include mobile-friendly versions? My audience will not be able to use the dashboard effectively on mobile devices. Considering this, I'm wondering if it is even worth investing in mobile UI optimization? Tending towards allowing sign up on mobile but rest of the setup can be done only on desktop. What are your thoughts? Looking fwd to your inputs :)