Why can't Avast Backup purge the old info that have been backuped?

Google Drive starts to warn me my storage was full.
Then I realize that Avast files was taking 22,4Gb :o
Of course I don’t have:
2689 contacts
106 phone calls
81 SMSs
3448 images
1039 audio files
39 videos
and, for sure, 1328 apps :frowning:

I’ve deleted the folder from Google Drive and will have to backup all over again.
We need to purge old backup data and can’t kept every single version of installed app and contact, to say something…

By the way, Android M will backup app and its data for free (maybe only configs and “small” data, but anyway).
Google Photos give free storage to photos.
Contacts could be automatically synced with your Google Account.

What is the future of Avast Backup?

Hello?