GBAS or GLS approaches do need a ground station and are currently approved for CAT I operation although they actually can support CAT IIIb to at least the same level an ILS can. Additionally one ground installation is enough for all airports within roughly 50 NM and can provide several different approach trajectories at the same time, which makes it more cost effective than an ILS, which costs roughly €20 Million per landing direction if a CAT III installation is needed. Slightly cheaper for CAT I only. But of course the downside is the requirement for a compatible multi-mode-receiver onboard the aircraft which costs a lot for A320 for example, but is standard on newer aircraft like the 737NG and MAX, A350/A380.
RNP approaches are of course much cheaper for airports as they do not need ground equipment and all current tech aircraft are equipped for it.
Airlines still plan for ILS as standard and lobby for its installation wherever they base aircraft or fly a lot, simply because the upgrade to low vis operation is fairly standard and a well done exercise.