I see it being mainly there for "last minute shoppers". Someone who has a get together to go to or a trip they didn't fully pack for while they are still stuck in the office. Place an order on Mr.Porter while at your desk and get the product in only a few hours. Show up at party, make profit.
Working retail I run into many people who are shopping for an event that night. I hate being in that predicament but it is good for the store as customers are bound to settle much more.
This. I've run into occasions where I've had to settle for something not exactly what I wanted, but I needed it that day for an event so I was stuck shopping at local shops. Things come up in real life, and some people may need stuff delivered same day. If you live in NYC and don't see your own need to use it, that's fine. I'd rather a store have more options to cater for customers, than less options.... Especially since the majority of MrP pricing is competetive (at least for the brands I shop for there).