Hi dude,
We do know some things can actually change the blueprint (hard radiation for a start) but this does indeed seem to be a common misunderstanding among those who discuss epigenetics.

The biggest problem so far though is that most people have never heard of it and can't imagine such a thing. The gap between current discovery and human awareness is now huge (and getting bigger). There are not enough points of similarity between what people know and this new information and it can't be processed. This 'gap' and the attendant fear of change may be the biggest factor affecting human development. People either just don't get it, or refuse to believe it. It's like going back in time and trying to explain the earth isn't flat, or trying to explain to creationists how evolution happens. Proof is just denied.

People who don't take part in the 'time machine' of culture (eg, read, write, listen and learn) -and that's most humans- are literally stuck in the past, believing what was believed in the past. The more we learn, the bigger this gap gets (perhaps the only downside to learning is at some point most of what you know, nobody else can comprehend?) But hey -imagine how Darwin felt! LOL  :  )

Plus there's the insecurity (maybe for some, shock) of discovering that most of what we believe is not true. Those who study science maybe get used to finding out that what we thought was provably true last week or year now provably isn't, we don't feel personally threatened when that happens because it happens all the time, but many folks rely on the security of believing most things they are 'told' are reliably (and permanently) true.

There's also the embarrassment factor. Nobody likes to discover they've been conned. I think if I'd spent ten years dieting & exercising and some dude said 'all you have to do is turn off these genes', I'd feel a bit of a dumbass. Nobody likes feeling like a dumbass.

Saying we can alter gene expression also implies self responsibility and that's something some are not at all used to. My neighbor for example believes that if we get ill it is the doctors' problem -that's what doctors are for. Self-responsibility is not a popular concept -she might have to start considering that her current obesity may in some way be her own 'fault' (she still thinks in 'blame' and guilt terms); and that takes away the anxiety-pacifying belief that one is a victim.

So not everyone sees epigenetics as a marvelous opportunity  :  ) fortunately it is a hotbed of new research and those who want to learn have more resources than ever before, all hail the internet.
Best,
AR