Because then it would be a question of why those abstract non physical things didn't exist in reality. We always have to be cautious about that-- there was a time that imaginary numbers were thought of as abstract and non physical, but it turns out they are absolutely essential in describing our universe. Even beyond them, quaternions are essential to relativity and for a unified theory of everything combining both relativity and quantum mechanics, 8 dimensional octonion numbers seem to be required. According to Tegmark, anything that is mathematically possible should be reality somewhere within the multiverse.
That sounds like a respin of platonism.
It definitely is common amongst mathematicians. Especially those who seek a unification of the infinite with the finite. Godel was one its vocal proponents.
https://plato.stanford.edu/entries/platonism/
Platonism is the view that there exist such things as abstract objects — where an abstract object is an object that does not exist in space or time and which is therefore entirely non-physical and non-mental. Platonism in this sense is a
contemporary view. It is obviously related to the views of Plato in important ways, but it is not entirely clear that Plato endorsed this view, as it is defined here. In order to remain neutral on this question, the term ‘platonism’ is spelled with a lower-case ‘p’. (See entry on
Plato.) The most important figure in the development of modern platonism is Gottlob Frege (1884, 1892, 1893–1903, 1919). The view has also been endorsed by many others, including Kurt Gödel (1964), Bertrand Russell (1912), and W.V.O. Quine (1948, 1951).