My Father is watching Egirls and Bikini streamers behind my mother's back.

I have been living with my parents for a while as I have been looking for work, but I've noticed my father doing some new strange things. He recently started watching this streamer who plays guitar on stream. She dresses quite skimpily (which is fine, I really don't care) which is what made me suspicious, my father is the type of person who only really engages with his hobbies and browses forums or youtube all day so it was weird to me that he suddenly watches this new streamer often. I looked into his search history to find out who this person was only to find a couple other people who he had been watching under the "pools" tag on twitch. Needless to say he was watching lots of women with their bodies on display for all to see. If this wasn't my father, who is still married to my mother, I frankly wouldn't care. I just feel like my mother would probably like to know that this is happening. I don't suspect my father of cheating or anything like that, but I also am concerned as to why this is suddenly happening. I also am worried that me bringing this up would cause a lot of problems and they've been happily married for a long time. I'm leaning towards keeping this to myself but part of me says that my mom deserves to know. Please help.