They are trying to appeal to a demographic of customers who wouldn't set foot inside M&S in a million years.
Whereas their formerly loyal customer base of middle-aged+ shoppers who'd buy plain black court shoes, cardigans, socks, underwear & bras, nightwear, basic trousers & shorts, nice summer dresses, work clothes, sandals, the occasional handbag and all manner of general clothing items are no longer catered for.
I can't remember the last time I bought anything other than a sandwich in M&S.