That’s what cables are for…It can’t possibly be that common for a home lab user to be hot swapping disks, so for the few times every decade when it becomes necessary I don’t think it should be overly burdensome to have to fiddle with cables and curse under one’s breath that a backplane would make things easier.
Since even the cables to interface between an HBA/motherboard and a backplane are so damned expensive there’s probably little financial incentive to prefer a backplane over a fistful of 1:1 drive cables.
So if the financial and ease-of-use arguments are essentially moot then the only remaining argument in favor of a backplane is airflow. I won’t hazard a guess as to the financial or effs-given value of airflow but I assume for the vast majority of homelab users the 3d printed drive cage would probably be preferred.
Have you ever had 8 SSDs hanging from cables inside the case before? Sure one or two that's fine. You start getting above 2 drives you start running into all kinds of issues, such as power splitters and all the wonder they are for drive placement. Not all cases have room to mount 8 plus drives, even using the 3M tape method.
The most inside a case I ever just dangled was 4 drives. It worked but when that MD array lost a drive its was quite a bit harder to replace it. That was with regular SATA cables and a couple power splitters.
Inexpensive Icy dock makes life quite a bit easier. Its still cheaper than a 3D printer and having to fiddle with that. Cable management in the case on the Inexpensive icy dock is still painful, as it can be spaghetti whether from a HBA or on board controllers. Biggest benefit is power and placement, followed by easily replacing a failed drive.
All im saying is its really impractical to go beyond 4 drives in typical cases using cables and tape. Sure if I bought a Fractal XL and some 1200w power supply maybe its not a big of an issue but for most users the Icydock is helpful.