The word simple has gotten a bad rap in recent times. We either think of it as a psuedonym for crappy or ugly or a nice way of refering to the developmentally disabled 30 year old who lives in his mom's basement, rides a bike and does handywork/ semi skilled labor. I don't see it that way.
Some of my favorite things are simple. One of my favorite meals is a good steak served medium rare with nothing on it, a potato with some fixings and some vegitables. My favorite drink is Scotch (blended typically but occasionally a single malt if I am celebrating or feeling fancy) with a handfull of ice. In a pinch the ice isn't essential. I like simple guns like AK's, Glocks, pump shotguns and double action revolvers. It is hard to beat a plain black wool pea coat.
When it comes to saving and investing simple things make or break you. If you simply live on less than you make and put the difference (after setting some aside for a 'rainy day') into a diversified set of instruments that make money things will go quite well. The way people mess up isn't by (assuming reasonable diversified choices) going with the wrong stocks or mutual funds or whatever but by not putting money away. See it is really simple.
I don't think simple vehicles or homes are a bad thing either. A simple reliable vehicle that will run reliable and get you where you want to go is a good thing. Often with reasonable planning you can (GASP) actually pay cash for them. Personally I would rather have a simple home, that I can afford to pay off in a reasonable amount of time and have money to save for the future, fund my child (and his planned sibling yet to be born)'s education and to be comfortable instead of having some cheesy wanna be Mansion which leaves us stretching and straining every month. It doesn't have to be a shack (though a small cabin or cottage if your family situation fits in it) but the idea of a normal modest 3-4 bedroom house with a couple normal bathrooms has slipped away recently. Not that a big house is bad if you can actually afford it but most folks, me included, can't. Why people set themselves up for failure buying stuff they don't need to impress people they don't like escapes me.
Simple plans are best too. It is said that a simple plan boldly executed will consistently give good results.
My point is that simple things are good. We rarely get ourselves in trouble by doing something in too simple of a fashion. Ever heard of that highly paid doctor who got himself in huge trouble by purchasing and living in a simple little house? I don't think so. Ever heard of an average Joe who got himself in trouble purchasing and living in a McMansion he just couldn't afford? I think we all have to realize that starting with a simple foundation and then, if we are truly able maybe expanding a bit is a prudent course of action. However I think that once we get past the silliness of it all, many folks are pretty happy with simple things and even when able see no reason to move away from them.