From the UK here, but you are at a significant disadvantage when selling a family home if there is no bath.
In this case, shower can be converted back to the bathtub, for not too much money/time.
Besides, once the house is sold, usually some interior changes are made by seller and/or buyer, e.g. new paint inside, new appliances, furniture etc, which all takes time and money and converting the shower would be just one more thing to do, and a relatively cheap one, too.
Yes, you can put one in for not a massive amount of money, but that's money that the buyer will want to knock off, or they'll just go for the myriad of other houses that DO have a bath.