3 and half months old chicks still have a lot of growing to do. Most breeds don't start laying until about 6 months old. Some might lay at 5 months. Once you see the combs start pinking up and developing, eggs are only a few weeks away.
At 3.5 months, they're not freeloading, they're maturing.
As said, it depends a lot on the breed. But even fast maturing breeds won't usually lay eggs till 20 weeks. 17-18 weeks is about as early as one could expect but 22-28 weeks is more likely.
The longer they wait to start, the fewer problems they'll have down the road. Laying an egg a day is like a woman having an 8 pound baby every day - give them time.
Yes - I'm on my third year with chickens. All that I have raised from chicks started laying at 18 to 26 weeks, with the Black Sex Links being the early layers and my Buff Orphintons being the late layers. My RIR hens started at about 22 weeks. My EE hen started along with the RIR hens. The cochins and Brahmas were late layers too.