Equally the LoCo's have shifted their business model more towards the traditional carrier's style; hence we are talking about reserved seating, premium this & that, flexi tickets etc. etc.
The low-cost carriers have not changed their business models. EasyJet and Ryanair are just trying to grasp a greater proportion of the market through offering services that will attract more business passengers or families etc. Rolling out some of the services that traditional flag carriers have adopted for years is their way of doing that.
To say low cost carriers have shifted their "business" model more towards traditional flag carriers is not true. Fundamentally their model hasn't changed. As EasyJet for example said countless times when rolling out allocated seating, if they couldn't achieve quick turnaround times or high asset utilisation which drives their low-cost model (very unlike flag carriers), then they would have scrapped the idea completely.