Oyster gateline display "Low Balance"

I also noticed this, probably a new scheme to make more money, targeting people not so familiar with the system, especially foreign tourists.

Seems to me a clear warning to top up.
Cannot see how this message can "target" tourists.

TfL seem to think that any PAYG balance below £10 is a 'low balance'. The auto top-up threshold used to be £5, but it's been £10 for a while now.

It is not crazy - you need to set the warning in the context of the maximum peak single fare that can be charged. - currently £9.40. The system has to cater for the worst scenario which is to give some small headroom above the maximum chargeable fare. Every time fares increase and / or the number of stations increases then these limits become higher and higher. A lot of people wish to see Oyster expanded here, there and everywhere but there are limitations in every system. The more TfL reaches beyond its area then the higher fares get. Imagine how much Shenfield to Maidenhead is going to cost in 2019!

I know a fair proportion of Oyster users work on low balances and regular uploading of money and I can see your point that for them repeatedly seeing "low balance" will get irritating. However a gate or a validator can't distinguish between card holders!

The move to contactless bank cards potentially changes things because the only limit is the card holder's bank account balance. However I believe there will be a strong resistance from some people to the idea of allowing TfL "free access" to their bank balance by divorcing journey charges from what they can see as they travel. AIUI bank cards are not written to so an exit gate will not show the fare charged for your journey. This all disappears into your on line account and the total charge, including caps or "standard fares", won't become visible until the data is processed remotely and someone logs into their Oyster account (I'm assuming TfL will provide this info) or sees their bank account statement (or online).

It makes me wonder if TfL are subtly are trying to get Oyster users to have more than £10 on their card? Having "Low Balance" instead of the total will panic many into unnecessary top-ups when most of my top-ups are under a tenner, either to reach the Z1-3 Oyster cap off-peak or for local z2-3 journeys.