I've been into this for 30 years now, at first I thought of myself definitively as a DL then in my early 20's I started getting drawn to more "babyish" things, I began to enjoy ABDL material (vids, pictures, stories etc.) and I wanted bottles and sippy cups, kids shows, bibs and clothing and all the stuff. I was particularly drawn to a lot of the "little" dresses, so many of them are just so cute, I think this may have been because most of what you could find as clothing for ABDL's at the time was geared more toward sissies it's only really more recently that there is more male or gender neutral stuff available.
So I began to explore the little side a lot more, buying nice things and enjoying the exploration.
I even bought a couple of those cute dresses, for a bit of background I have always been a bit more effeminate than other boys my age and don't have the same interests as most of the boys as I grew up, but I am not TG and don't really have any interest or thoughts of being a girl in generall, I am quite happy being a guy.
For a while though I thought it would be nice to have someone treat me as/make me a little girl, just to see and explore that a little bit. As a bald guy though I felt weird in the dresses without nice hair to go with it (tried wigs, didn't work well and don't like them), never found anyone though.
As time passed and I explored more I came to the realisation that while I like many childish things I never really felt "little" more like an adult just pretending or acting in a role, I still enjoyed others indulging in the AB side and still have bottles, sippies, paci's, onesies etc. and would like a certain few items of AB furniture (like a decent highchair) I still use bibs sometimes when eating a potentially messy dinner at home. I also enjoy going to ABDL play events when I am able but I don't really regress or see myself as a little, more like a DL with childish tendencies and the dresses haven't come out for many years now.
As I have gotten older and more over the last 8-10 years I have found myself much more drawn to the daddy or CG side, this may in part be due to my career in the care sector but there is also the fact I still enjoy the AB side its just more that I like the idea of supporting someone else to explore their littleness and as you said being trusted with the intimate care and deep feelings of another person.
I imagine if the right person came along who was not only willing but also experienced enough to support me exploring properly I could find myself enjoying being little a bit more but it would probably still not be very often. I do still wish there was less stigma around guys wearing skirts though as they are a supremely comfy item of clothing in the summer and make changing nappies so much easier.
So it could partly be an age thing, wanting to explore the CG side, it could also be down to more experience, or perhaps stagnency of the same things and wanting to spice it up by exploring a new role, maybe there is always a maternal/paternal side and something else triggers it to come out. There will probably be different reasons for different people, and not everyone will experience the desire to be a CG just because of aging.