I’m not aware of the exact motivations of all the actors. What follows are my guesses.

My guess would be that

• Some député want to protect children from the most dangerous types of porn (which I can hear on some level, porn can be addictive for some people and can lead to negative behaviour, children are always more sensitive).
• Some probably think that all porn is bad and want to prevent anyone from consuming it, this would only be a first step for those.
• Some definitely want to be able to spy on everyone and use this as an excuse to further reduce privacy and freedom

You might not be aware depending where you are from, but France is on a slippery slope towards Fascism, the far right is gaining more power every day, a lot of people think it is very plausible that a far right president is elected on the next election (2027), along with a parliament’s majority.