We aren't comparing apples to apples. It is a different button with different meaning.
The barrier to my "liking" something is substantially lower than my "favoriting" it. I understand both, but I'll do more of one than another.
The real question is what the goal is and whether user are getting more value from more likes versus fewer favorites.
Are my interactions 6% more engaging? Does the quantity of interactions cover the decrease in quality of meaning?
Subjectively, I don't feel like it. Favorites had more meaning to me than Facebook likes precisely because there was a higher bar. They've diluted the meaning of a term and are, unsurprisingly, seeing people use it more often.