I would choose a different brand if the tea bags came as plastic and send them a nasty letter. I've been lucky enough to never have encountered them I guess.
Honestly I find some of the "nicer/high end" or even organic brands of tea sometimes use the plastic sachet, this is because that allows you to see the product inside whereas the other ones hide the product. The only brands I run across with it lately are Harney and Sons, and a Russian tea brand Maiskiy, but most Maiskiy bags are paper. And Harney and Sons is a nice treat.