I truly do feel sorry for you part timers on here that are trying to make a difference. But I'm going to be honest with you.
The situation hasn't changed for 30 years. I could sit here all day and give you a dozen different reasons. The part timers just have never united.
The part-timers are "united". They are united in a union called Teamsters. They pay hard earned money for a union negotiator to negotiate on their behalf. Just like any other service you pay for, you are paying someone to do something for you (many times because you don't want to do the dirty work yourself). And lets be realistic, we can't have 100,000+ union members at the negotiating table all at once, thus we pay a union to negotiate on our behalf.
If the union was "truly" concerned with what the part-timers wanted they would find ways to get feedback from them. This is the 21st century and there are more constructive ways than "union meetings" to get feedback from then. Here in my area they mailed out contract surveys to all the members in our local to get feedback on what was most important in the upcoming negotiations. And I hope they do the same thing all around the country. How hard would it be to have a shop stewards ask around the part-time ranks what they want out of negotiations and then report it back to their local union hall?
the current work force isn't the same as it was 100 years ago. We dont all have schedules that revolve around the 9-5 / mon-fri work week, thus its unrealistic to think that everyone can meet at a specific day/time for a union meeting. When I was part-time, I found that almost every union meeting conflicted with my twilight shift and/or sat driving shift. And now as a FT driver I find that EVERY meeting is catered to my FT work schedule.
The Teamster have more than enough money and resources to find ways to communicate with its part-time members. And they should be obligated to find those ways after receiving so much union dues from them.