Unfortunately, most plastics are useless to recycle - they either get incinerated or dumped straight into the landfill by the companies who collect and filter them.
Which is why my wife and I only bother with plastic bags, styrofoam, and the hard plastics marked types 1 & 2. These are the plastics which are easily recyclable, and therefore, have a non-trivial chance of actually being recycled.
We put types 3 through 7 straight into the trash, as they have about a 97% chance of not actually getting recycled.
Plastic bags, styrofoam, and those hard plastics marked types 1 & 2 are the ones most likely to be recycled into new products. They are easy to break down and recycle into new containers.
Hard plastics marked types 3 through 7 are most likely to be filtered out and either incinerated or dumped straight into the landfill, as it costs more to recycle them than to just create new straight from oil.