They can’t be large DSLR style interchangeable lenses because of the form factor. Nor can a single tiny lens even have the range of a compact digital camera because of the form factor. But by adding extra lenses to cover different focus ranges, a smart phone can replace the compact digital camera device. They can’t be as good as a DSLR, but I haven’t needed anything but my phone and DSLR in years where before I bought a new compact digital camera every few years.