Most people transiting LHR don’t clear the Border and enter the UK CTA, and so they don’t encounter the egates. The egates are relevant for those entering the UK-Ireland CTA but not to most passengers transiting LHR.

Even for those visiting London, lots of Americans can’t use the egates at LHR — as again became evident on Friday and Saturday at LHR T3, T5 and T2. The UK has blocked egate use at least for passports beings used by kids who are under 12 years of age.