One problem with fast writing is that it requres more energy to transmit from reader to a card in order for a card that has no internal source of power, to toggle bits. It is harder compared to just reading a bit from a card. Additonaly it is tricky to implement trasaction with single write, given that data transfer can be interrupted (for example user removes card from RF field). I am not sure if single write is enough for making this robust/transactional. It also helps a lot if RFID antenna is well tuned. Proximity of metal and way it is mounted has a big impact, so it is important that RF antenna for reader is tuned for exact environment it is mounted in.