Comment by AlexandrB

This is true about other things like reading speed as well. It still doesn't mean that time limits are useless. These are skills you can develop up to a reasonable level through practice if they're lacking, not something fixed like height. And if it takes you 12 hours to get through a 2 hour test because of these factors it's a sign that you're not going to be a very effective employee/researcher. Being able to read/write with some haste is not unrelated to job/academic performance.