"The nice thing about standards is that there are so many different ones to choose from."
Or, in cartoon form:

Ha ha. I will try to list 14 standards to justify a need for 15th one.
1. LXI … No thank you, I will keep my money for myself and sanity for a real job
2. Desktop PC … No, it is shelf thing, should be small and I have no 8 projects to fill it, only 4 at most.
3. 19 inch Rack … No, it is shelf and very shallow and narrow one. Also there is no that much money I am willing to spend on metal and shipping
4. Arduino … No. Is it even a backplane ? How do you address the shields when you have more than one ?
5. USB hub with star of cables … I already have it and I am not full time writing high level software or Signed Certified Device Drivers, thank you
6. Kamak … Too high, it is named "Crate". I don't live in nuclear bunker next to particle accelerator
7. GPIB … I can possibly build things that can fit inside this connector alone
8. Eurocard … No, the backplane is rigid and pinout is taken for who knows what purposes, but I will take your aluminum profiles for panels with screws if sold for reasonable price.
9. PC104 … No. It looks like very expensive Arduino
10. PCI-Express … No, I am too old to learn FPGA and too poor to pay for identificators or whatever is there involved, I only need few bytes to bit bang
11. Automotive Radio Formfactor … No. Too small to be a crate, too large for single project.
12. Some random HP or Tektronix frame... No the formfactor is there, but size is unyieldy
13. VME .. No. It is vertical and obscure
14. Some other standard I am not aware about … No. Because that is exactly the reason: the fact that I am not aware bout this standard.
Conclusion: need the standard number 15