to think that shoes should be a bit more durable?

I bought these sandals at lunchtime from our local shoe shop. DD wore them straight away, and walked round town for two hours in them.

I was surprised to see that there is already quite a lot of wear at the heel and a bit at the toe. The soles are soft rubber, though obviously I didn't realise quite how soft when DD chose them. They are Mod8 ones.

I'm a bit concerned that they will now wear out really quickly but I don't want to go in guns blazing if it just turns out that DD has a funny walk or that it's normal for rubber soled shoes. AIBU?