More often than not, most of the stuff I've read that doesn't pass the common sense "sniff test" tends to be based on ridiculously flimsy evidence.
Raw fish consumption in pregnancy is actually recommended in certain countries (Japan being the most notable one). The salad thing is not something I've heard, but a quick Google search shows sources from Singapore, the UK and Australia (except for NSW, for some reason?) all claiming it's perfectly safe.
Going a bit further, the egg thing is based on a single case from the 1950s, follow-up studies on women who got the chicken pox vaccine while pregnant shows that they had a _lower_ incidence of varicella-induced miscarriage, and there's also no evidence that children will get sick if you make their formula using properly treated tap water from a metropolitan source. People in Spain and Italy regularly have a glass of wine with dinner while pregnant; they just don't get shitfaced and everything is OK.
I don't know why all of this pleasure-sucking, stress-inducing bullshit "advice" is accepted by anyone, but I suspect it wouldn't last long if men were the ones who got pregnant.