It isn't just a question of being out of date. At first, the increased baggage limit was only available at a small number of airports, including Heathrow, but either Stansted or Gatwick was excluded because new equipment had not yet been installed.
Plus, some airlines - notably Ryanair - simply do not intend to take up the option of allowing heavier carry-on luggage. Ryanair remains one item, 10kg, 55+40+20cm.
I was recently charged £18 by Ryanair to check the bag I intended to carry on because it was 2cm too thick (22cm). On the return journey (from Ireland) I said nothing and was allowed to carry it on. ;-)