There are 0 reasons to have both RPM and DEB systems. Just a mess for maintainers with no real advantages for end-users in having one instead of the other. If there were real advantages of one over the other, then just adopt the best one. Instead no, we have to have 2 systems just for the glory of uknown anti-end-user reasons.
To make it short: We all know DEB is better than RPM, the problem is that Red Hat, the biggest commercial Linux solution, for historical reasons uses RPM. And for this reason, we still have RPM. I call this an issue.
Let's not even mention all the other packaging systems. Each of them says "Hey, mine is better than yours". Sure sure, yours is of course longer than mine. If everyone think like that, today there would be 0 international standards. And this is why I just hate that each "major" distro has its own way of doing its packaging system. Sure, once again, yours is of course longer than mine. They all say the same thing.