I think it is very easy to get dismissive, jump to a conclusion and move on when you see a flower. I know I do it, I try not to but I still do. With rough hawkbit (Leontodon hispidus) it is so easy to just dismiss it as a dandelion when, in reality, in the right environment it can be far more numerous than dandelions will be in their preferred environment.
Rough hawkbit and dandelions are closely related, they are both of the Leontodon genera, sub-species of the daisy family. They both have that classic yellow dandelion flower which turns in to a fluffy 'clock'. They both have a basal rosette of leaves which are toothed (dandelion - dent de lion - lion's teeth). However, there are differences if you look. Rough hawkbit has a hairy stem, the dandelion smooth. Rough hawkbit has a green stem, the dandelion often tinged purple or brown. Rough hawkbit has a smaller and much tidier flower as dandelions tend to have untidy sepals that turn down under the flower. There are other small differences too if you have a book with you to help you identify the two of them.
Now here is the key for me, the answer lies in the soil! It is not possible to look at every low growing yellow-rayed flower to see if it is a dandelion or rough hawkbit. If you are on chalk or limestone grassland then expect rough hawkbit, if you are on heavier, more fertile soil (like my lawn) then think dandelion. I think I am right in saying that you are unlikely to find the two together so once you have identified one, the masses of others nearby will almost certainly be the same.