I once went to an Israeli family for shabbos, so you can imagine all the chumus, tehina and other Israeli foods we were fed. I was repulsed when I saw the hostess washing out all of our plastic ware. Forks, knives, plates, cups – you name it!
Rest assured, our plates felt quite slimy the next day. Ugh, washing plastic utensils are a big nono.
Most people buy plastic for convenience, the convenience is to throw them out. If your already washing them out why not use regular dishes?