They could, but tablets are lighter, more maneovarable (spelling?), easier to store, and dont need cable running across the floor to plug in all the time, more intuitive (we've had loads of laptops before, the batteries only ever seem to last about an hour). Believe it or not we still have students who refuse to use computers because they dont understand them, but are quite happy to do the research on their phones and write it into their books..... Tablets are just scaled up phones tbh.
And we'd get mega kudos with ofsted, parents and governers.