Yes, I understand all of that and if I was a regular Tui customer I'd go for the voucher. They just happened to be the only airline flying from BHX to Heraklion this weekend when we planned to meet up with my brother-in-law and his daughter coming over from Germany. There is absolutely nothing wrong with Tui but this would have been the first time using them in 5 years (previous was again flight only).
We have tickets booked with Eurostar and Deutsche Bahn this summer and if we still can't travel then, then I'd take a voucher as I use both every year and appreciate that these are tough times for all travel providers 👍