Here's why:
* "Affectionate" is already an adjective expressing a high degree of fondness or love. It's hard to make it "more" affectionate, like you would with "big" becoming "bigger" or "beautiful" becoming "more beautiful".
Instead of comparatives, you can use different adverbs or adjectives to convey different degrees of affection:
* More intense: *deeply affectionate*, *intensely affectionate*, *passionate*
* Less intense: *fond*, *loving*, *warm*, *caring*
* Extreme: *adoring*, *devoted*, *obsessed* (use these with caution, as they can have negative connotations)
For example:
* Instead of saying "He was more affectionate today," you could say "He was deeply affectionate today."
* Instead of saying "She is the most affectionate person I know," you could say "She is a very loving person."
Ultimately, the best way to describe affection depends on the specific context and the intensity you want to convey.