Sure, you clould just fix checkboxes. But then you have to deal with select boxes, which also work badly on smartphones.

Then you have the modern smartphone-driven practice of using multipart forms, with one field on each part. You can't see the whole form at once; you eventually find out that the very last field is a date-field with three badly-behaved drop-downs that you can't interact with.

I just don't try to fill forms on my smartphone. In fact I only use it as a (shock!) phone.