Removable tray isnt exactly necessary. Most cases nowadays hold between 5-8 hdd's with 2-3 SSD slots. HDD's usually are only held by 4 screws or 2 quick lock tabs. So not like it is time consuming to add or remove a HDD, unless you consider 5min a lot.
Alright, what about for upgrading GPUs and CPUs? Removable mobo tray not necessary?
Swapping out GPU's is relatively easy as well, 1 screw, maybe a quick lock and 2 power cables. CPU is a lil more complex with a Heat Sink Fan, but the HDD cage usually never interferes with any of those. Honestly, i dont see any time worthy advantage of having a removable HDD tray. if you are getting a fairly nice case, that costs a decent penny, you are more after cooling, cleanliness of cable routing and bells and whistles of USB, fan controls and those cases are generally large enough to have plenty of room to work with.
IMO, no need for a tray, but that is just me...