Factually you are of course right, all virtual cards from HDFC, SBI, ICICI are not working. But the justification doesn't make sense. It was never BoB's job to sustain Amazon's business model. If the cost to BoB's servers was to much due to people generating lots of cards, they could have charged for it. ICICI, HDFC and SBI have much bigger server infrastructure to absorb that server cost or to make it an additional profit center - still they don't do it properly.
As for generating lots of cards, that used to be the stated purpose of HDFC virtual cards : use them one time for one shopping, and then forget it. Somehow all banks have secretly stopoed supporting them, without declaring explicitly.