nottoday Your pithy little strikethrough, although it made me smile, is a non sequitur.
The city of London is unique in the UK for its transport system and for its, ahem, robust commuters. If you take the underground in glasgow, or the tram into manchester, you're not likely to struggle to get a seat to nearly the same extent, even at rush hour.
When I used to get the central line to work in London, getting on at liv st or bank I would find that it was already packed to the gunnels, and would jump onto the train and slot myself into whatever tiny gap I could find- unless you had an eye level badge on, nobody would be able to see you were pregnant.
This kind of commuting just doesn't happen in every single town and city across the country, hence the lack of need to roll out the badges elsewhere.
Not everybody has a pregnancy which, although difficult, means that standing for their commute is possible or desirable. you are rather lucky.
In terms of London commuting, I would rather that more employers introduced better flexible working so that pregnant employees can avoid rush hour travelling at all- I struggled as a non pregnant person with asthma and slight claustrophia, so the stress to pregnant women must be intolerable.