First off, let say up front that I realize that someone is going to misread what I say here, and probobly jump in and call me a racist. This is not true at all. If I thought this was a race issue, there would be nothing to post. This is a subject that gets interesting when you look beyond the surface ( “oh, blacks do such and so” ) and try to find the root cause of the problem.
Just FTR, the term “lower class” throughout this post, refers ONLY to economic situation
In my job, what I do is to call on clients to represent and sell small business benefits and discounted health insurance to self employed people. I spend the first part of the week phoning people who have inquired about what we have to offer, making appointments, and the second part of the week I actually call on them at the times specified. What a lot of people in my line of work will say, I’ve heard it before, is that black clients are more likely to stand you up than white ones, that is, make an appointment for a certain time and then not be there. On the surface, this apears to be true, anecdotal evidence only. BUT…it’s not. When you are dealing with people who could be considered economicaly middle or upper class, they are not likely to stand you up, no matter what hue their skin is. So maybe it’s an issue that is linked more to income than anything else. I think that’s the case. This brings up the first question I have here: To what degree is the ability to schedule business appointments, and follow through on them a prerequisite for business success? I tend to think it is of paramount importance, and perhaps these businesspeople are not poor time managers/appointment keepers because they are lower-middle or lower class, but are in that economic situation because they have poor time management skills. Opinions?
Ok, now that leaves race and culture. Now even among lower class people in general, I have found from experience that blacks are more likely to make appointments and not keep them than whites, although frankly whites are no great shakes in this area either. Why would this be? The color of skin has to do with only one thing, and that’s a climatic adaptation to sunlight, basically. Using that as a basis for behavior is stupid, unless you are comparing the likelyhood of sunburn in July. Two thought come to mind here. Number one, I live in urban, northeastern United States. The number of lower class blacks here is greater than poor whites, so I am going to interact with more of them, just by sheer numbers. If I was working in, say, West Virginia, the situation would be flip flopped, I have no doubt. That leaves us with…culture.
Or should I say sub-culture? We all live in America, so that is the uber-culture. Beneth that though, there are certain sub-cultures, African-American, German-American, Japanese-American, etc… These have historically been based on ethnic origin. Most of the white sub-cultures have homoginized to a large degree over time, but black sub-culture has remeined somewhat apart from the others, no doubt because there is a visual difference that is immediately aparent to see, dark skin vs. light skin. Even there, It has been my experience that middle class blacks live and act pretty much the same way as middle class whites, but I’m not sure the same can be said for lower classes. This troubles me to some degree. I have observed, among some poor blacks, a cultural bias against success. Children who excell at school are often acused of “selling out” ( selling out what? poverty? 
). People who befriend whites may have to deal with being called “uncle toms” or other not so nice things. Here in the NW, where there are clusters of very poor people living in one place, a welfare mentality of “gimmie, gimmie, gimmie, I am owed money and support without being required to do anything” atitude is rampant. ( To be fair, I see this exact same atitude among whites on welfare too. I think it’s a by-product of being human, and having stuff given to you w/o learning you need to earn what you get) What troubles me is how this impacts the population as a whole. In my mind, it adds up to a signifigant portion of the population that not only has to deal with the lingering disenfranchising effects of 300 years of racism, bigotry and slavery, but is also in some ways doing it’s best to disenfranchise itself. There is nothing but trouble and conflict down that road. As I see it, it is this cultural atitude that leads to more missed appointments.
Boy, did this OP swerve all over the place! I tried to frame the questions in terms of my work, but I think the question of cultural compatibility and acceptance ( both ways ) in the last paragraph is perhaps more important. I would welcome any and all discussion of the topics brought fourth here.