....cause the dose is too high.
Of course, you CAN make it - there's a ton of synths at USPatand & EspaceNet, but all of them use some precursors that are very cheap/available industrially but completely out of reach from OTC point of view. Which are by no means easier to get than BDO. I know, i did a very thorough serach on this subj some time ago.
If you want GHB, try GABA route, but yet better (in terms of scalability) - oxidation of THF with Br2, Cl2 and such (generated, possibly, in situ).
Antoncho