Why they don't go in the yellow bin

Kerbside recycling sorting facilities are built around rigid materials — bottles, cans, cardboard. Soft plastic bags and film tangle in the sorting machinery, contaminate other material, and are a common cause of a recycling facility having to stop and clear a jam. A soft plastic bag in the yellow bin is one of the most reliable ways to contaminate an otherwise-clean load.

What to check before assuming a drop-off program exists

Dedicated soft-plastics collection points have existed at various times through supermarket-based programs, though availability has changed over time as individual programs have started, paused, or restructured. Because this changes, the most reliable approach is checking current availability directly rather than assuming a program from a few years ago is still running unchanged.

The safest default

If you're not certain a soft-plastics program is currently active near you, the general waste (red) bin is the correct default over the recycling bin — a soft plastic in general waste is just waste; a soft plastic in recycling is contamination that can affect an entire load.