Why won't my dentist bond my chipped tooth?

Your tooth has already chipped and then the bonding fractured. Replacing the bonding again will most likely result in another fracture. I would recommend restoring the tooth with a more durable, longer lasting solution such as a dental crown or veneer. I hope this helps. Click save on the save button below my name, so that you may ask me more questions in the future.

It depends on the size and location of the fracture/chip and it certainly depends on your bite (how your teeth come together) and any bruxism (clenching and grinding) habits that may be present.  Keep in mind that the most *definitive* approach to match (shade and shape) of front teeth is through veneers or crowns and they are less likely to fracture and chip off.  Keep in mind that dental bonding is much weaker than veneers and crowns.  I hope this helps.  

The first question is why did the tooth chip in the first place? Typically, if a bonded tooth chips quickly after fixing it, then your bite needs to be looked at. Maybe you grind your teeth at night when you're sleeping and when you do this, the bonding is in the way and can chip. Like you said, if you purposely want to, you can touch the front teeth with your bottom ones. This needs to be addressed when the bonding is done.