More lines are going "tray-less". Princess no longer has trays and they are gradually disappearing on other lines. It is a cost saving measure. Less cost for the trays and less cost for washing.
I personally don't mind it other than not being able to place the drink on the tray. On Celebrity they do have attendants who will assist you if you have a cane or are unable to handle the tray on your own. For me a single plate is far easier to handle, with one hand, than a tray.
A second trip for the dessert isn't a big deal but for those that have a serious mobility problem it could be problem.