I heard TfL were leaving it to an extent to try and show how badly the new trains are needed to central government - sounds like rubbish to me though
I don’t think there’s a single reason, but more a combination of factors.
TFL has been cash-strapped for many years, and effects of this can be seen all over. It isn’t just the presentation of fleets that has suffered, reliability has generally tended to decline as well. I suspect we’ll see more of this as it becomes increasingly apparent that a lot of the work done during the PPP years was to a poor standard, especially on the stations.
Personally, I don’t think it’s all about money though. My own view is that there’s also been a lack of focus from the top down, and presentation just hasn’t been a priority for TFL. Perhaps Khan sees shoddy-looking trains and stations as merely part and parcel of being in a large city?
One can also wonder what BTP’s role in all of this is. Graffiti attacks are pretty brazen nowadays, it doesn’t just happen in insecure remote sidings, but increasingly whilst trains are in service. No one seems interested in tackling this.
There’s a real “head in the sand” culture at TFL now, at times it feels like an organisation very much in denial. You might get very rich if you had a pound for every time one heads Andy Lord say the word fantastic, but it doesn’t make things true.