Trailer Trash

I am sitting in my sunny kitchen, sipping a cup of fresh brewed coffee, looking out at the trees that are beginning to change color, yet on such a calm afternoon I am feeling vexed. Earlier in the day, I ran into an old acquaintance from Brattling's ( fruit of my womb) childhood. After the first few "How are yous, you look good, whats new etc "she said in a very quiet voice "I have moved. I am ummmm... living in a trailer in Lakeview. FH and I have split. " Quizzically looking at her, I asked, so----are you happy? Replying in the affirmative, she then proceeded to tell me about her new home. She jokingly, ended the conversation with "Well I suppose I am now trailer trash."
This phrase has niggled away at me for the majority of the day. I simply don't understand it. Granted, I grew up on a farm, and always lived in a house of one type or another except for a brief stint in an apartment during my misspent and misguided youth. I have family members who have owned trailers, and lived in them while building homes, being in transit from one phase of their life to another, or have settled permanently. Money was not the over riding decision to move into a "trailer park". Rather a hatred for apartments, and landlords who became petty tyrants just because they could, were. Some of my relatives, (the trailer park ones), had more disposable income than 3 families put together. Their priorities were a safe comfortable place to live, with plenty of room, that required minimal upkeep and no condo fees.
So where do we get the phrase "trailer trash" and more importantly why? There are no "crack trailers", but there are crack houses. Every city has a plethora of run down unsafe houses in areas where you need combat training to stay alive long enough to get a quart of milk at the corner store. Yet, other than for " They don't live in the best area", there is really no universal stigma to living in a house that has no plumbing, heat, running water, and doors half off their hinges. Unacceptable yes, but have we ever heard them called " house trash" ? NO.
Again I ask, why do we as a society in general look down on people living and owning alternate housing ? Those who live in trailer parks, own their homes, pay property taxes, pay for utilities, and upkeep. In some cases they are even paying more than they would for a traditional dwelling per month, as lot rent is also added.
What is it about a "mini-home", "mobile home" or trailer that so offends our sensibilities that we have a special name for those residents? I simply don't get it. Can anyone enlighten me?