BA (and all the other airlines) have been unbundling things for years. But customers also do that. There are (very broadly) two large segments of holiday customers, those who want everything in one package and those who will carefully choose each element to get the best ‘deal’. Deal being price, loyalty benefits, payment terms etc.

IMHO an important reason to bundle up with BA was extra Avios. Now BA has assumed that the same principle will apply to nTPs. But the changes in levels for achieving status means that for a considerable number of people, the draw of nTPs is not attractive enough (insufficient nTPs to materially improve status) to make bundling a holiday (with BA) worthwhile. The benefits of unbundling and getting other benefits is higher, so that holiday won’t go to BA but will go elsewhere. YMMV.