A number of municipalities have already banned all helium balloons simply due to litter concerns. Major suppliers rationed helium sales as recently as 2022, after the Ukraine war limited supplies from Russia. Helium has often been the subject of proposed legislation for increased government management of prices or supplies, or special discounts for favored uses.
Now imagine a major new use – displacing nitrogen completely, for cognitive enhancement, for an entire work day – arrives. Some can tolerate traditional pressure regulators, but others dislike their bulk/discomfort – so novel delivery strategies, with more leak/loss (like full-room environments), proliferate.
Prices would be driven up for traditional (& government-favored) medical/industrial/research users. Helium leak detectors in industrial settings would face more false-alarms. Exhalation/outgassing would sometimes cause electronic malfunctions in neighboring offices/apartments. And even if almost everyone gets it right, someone somewhere will err in their processes, injuuring or even killing people.
New supply regulations against this novel, & politically disfavored use, would then be a risk – even if the net performance gains still significant.
As informative precedents, in the US, consumer access to pseudoephedrine, flavored cigarettes, & plastic straws has been noticeably restricted in the last decade, on flimsier rationales. It's become more difficult to acquire racetams & other nootropics in just the last few years. California is in the process of banning all gas appliances, despite a long tradition of cheap/easy access via household utility hookups.
So, while I'd hope you're right that no new restrictions on helium-purchasing would arrive, your certainty seems naive, in a childlike & history-oblivious way, to how reactionary supply-control regulations often develop.