Transformers are invaluable for audio. They solve many real world problems. Well made transformers are inherently quiet (they are passive) and have a very high common-mode rejection ratio (CMRR- this is how well it rejects noise in a balanced line), they can be run unbalanced without needing any extra help, can handle high levels without severe clipping and they have a great range of characteristic sounds and applications. However, good quality transformer cost a lot more, they are heavy and take up lots of space in circuit boards, and not as readily available. These are not things you could easily clone overseas. Although there are very well made professional transformerless designs, some companies have decided to try and make “transformerless” a thing to desire – this is not a move for better sound but to cut cost in parts.
Much of the older or “vintage” quality gear which contain tubes are sought after because of their great sound but the key factor making those units sound so good isn’t much the tube as it is a fact that older designs have transformers.
Nowadays “transformer iron” has become a marketing term but transformers are not made equal, and like many things, you can have good quality, poor quality, and everything in between. A well-made transformer, designed and applied specifically for the job it will do, is itself the most valuable component even after many years of use.