It seems sensible to me that a strip might exist that includes a return wire form the data so that you can have strips going in loads of different directions and not have to have your own data wire returning…
Or if you had a length and wanted several LEDs ‘dangling’ but still he addressable.
You could order custom strips like this if you needed them, but the downside is that the return wire cuts into the copper available for power/ground making voltage drop worse.
Depends somewhat on the style/form factor/density of LEDs you require.
For “seed pixel” style strings, there are a number of prebuilt options from 10cm down to 2cm spacing (30LEDs/m to 50LEDs/m). These have 4th “bare” wire that works well as a return line.
Once you get into higher densities and the “LED on a PCB” style strips, your options get more limited. As mentioned, it may be simplest to add a small wire (there’s little to no current requirement for the data line). Much will depend on your layout(s) and the max length of the data line you envision.
I used the wires from a Cat 5 patch cable as return wires for a project I built. The splice is protected with a goop called liquid tape and just used clear scotch tape to hold the return wire to the LED strip. If you just use the white half of the Cat 5 pair, it’s nearly invisible.