Every man needs clothes for just knocking about, and in the realm of tailored clothing perhaps nothing better fits that bill than a cotton suit. Whether poplin, seersucker or corduroy like Wes Anderson's jacket and trousers in the photo, the advantage of cotton is that it combines form with a casual air. It is also as inexpensive as these things ever get, which of course is not really inexpensive at all.
The disadvantage of cotton is that it does not wear as long as wool, and the tailoring costs the same whether the cloth is cheap or dear. But where there is a will there is a way, and cloth merchants like Scabal have found that by weaving some cashmere into their cotton they can collect almost as much as they do for good wool. That takes care of the cost side but, sadly, does nothing for longevity.
Still and all, when a man wants to look approachable without giving up his matching jacket and trousers the cotton suit is probably his best choice.