Here are a few possibilities:
* They might not feel that way yet. Love takes time to develop, and they might still be getting to know you better.
* They might be afraid of rejection. They may be scared of hearing "I don't love you" back, or they might be worried about ruining the relationship.
* They might have a different love language. Some people express love through actions rather than words. They might show you they care by doing things for you, being there for you, or giving you gifts.
* They might be dealing with personal issues. They might be going through a difficult time in their own life, which could be affecting their ability to express their emotions.
It's important to communicate with them and try to understand why they aren't saying "I love you." If you feel comfortable, you could ask them directly: "Do you love me?" or "How do you feel about our relationship?"
Ultimately, the best way to figure out why they don't say "I love you" is to have an open and honest conversation with them.