I would not say "DA pros." I would say average system administrators. Average system administrators know how to do this with or without DA. If you are not at least an average system administrator then you probably should not be running a server anyway no matter what the control panel is.
I think you missed my point, I have a custom setup on my company's NAS arrays that are mounted as /backup. The normal admin backup runs and the status email sends when it's done, that email is piped into a script that triggers the NAS system to move the backup to a dated directory for each server and wait for tomorrows backups. This is what we use on our shared/reseller hosting servers, and it works for *US*.
We also own a colocation facility with dedicated servers and we license DA for colo boxes, the problem comes up with the average users putting in support tickets asking why admin backups just overwrite daily. Most of these users can get around in shell, but they just paid us for a license, why should they be in there tweaking the backup system just to get more than one day of backups? Some of them check this forum and see responses like the above and assume it's just crappy software. This is where a lot of them say "well cPanel does this...", and unfortunately we don't have a good answer to give them, so this is the point where some of them actually pay more to switch to cPanel. The average user does not want to get into the server and start setting up custom cron jobs to handle backups, they just want it to work.
My personal opinion on it? When I buy a control panel license I expect basic features to come with it, the backup system is one of them. I expect to install a firewall, I expect to install other custom/non-standard services, but having to tweak the backup system into doing more than daily backups when it could simply be a check box somewhere? no
DA is falling behind when you compare it to a lot of other CP's, there have been no significant changes in the past few years. Sure we got Dovecot and some other stuff here and there, but the feature set is lagging behind and some of our users are switching because of simple little things like the backup system. Also how hard is it to get a simple mail control panel? cPanel had this for years, and DA still hasn't added it. These are the the little things that add up into driving away DA users.