I often see comments like "I can't think of a reason why you wouldn't ERF".
My reason is that we don't own a car. DD's group 1 seat (Kiddy) is for taxis, hire cars and lifts. When I bought it a few years ago, I thought it was the best option to fit pretty much any car quickly - I can't imagine myself faffing about with the passenger seat in a taxi to get the seat in contact, for example. The Kiddy seat is also light enough to take on the train and use a taxi at our destination, which is safer than driving all the way.
Would those of you have have ERF seats disagree with me? If there's an ERF seat that fits the bill, I might consider getting it.