I find it hard to get this sort of paperwork back too!
I just do what you're doing, use the info I get during drop off / collection chats. Then when I'm writing up the LJ for example. Photo of x playing with the Happyland church and wedding party. We talked about x's aunt and uncle wedding where she was a bridesmaid, who was there, party, food, flowers etc. People now have been named after aunt and uncle!
As a parent, I've never been asked to do this, and I really wouldn't have wanted to - it definitely would come under the category of "pointless paperwork" for me, and I get enough of that in my own job without it creeping into my home / family life as well.
As a cm & parent who has used a cm this sounds a bit OTT to me & I can understand why parents aren't replying especially if their DC are only with you PT as frankly most people don't have major (or even minor) events to report about every month and it can get quite tedious as a parent having to come up with things!!
I'd stick with verbal communication which you then note for planning purposes & try and follow the children's interests more. I'd also make written feedback requests less frequent as you're more likely to get a better response IMO . I have a feedback form that goes home termly with LJ's & have a section for 'At home I'm enjoying...' and you could always expand upon this & ask for them to share any events or milestones.
As a parent, I try my best to complete these forms, but often forget!! I am much better when the request comes in a different form. E.g.Can your child bring in a photo of an outing you recently enjoyed Can your child bring in their favourite game/activity/piece of art work etc
For some reason, I tend to remember these and, as the dccs bring them in, they are more likely to talk about the event/engage in the activity.