It’s too big
I find that people who say this frequently don’t have a firm idea of what is too big or even why it might be as big as it is. This also goes in with the I need to free up disk space with no good reason why the space needs to be freed up.
There are good reasons to shrink the log and they do revolve around space. For example:
I had a one-time explosive growth of the log due to a large data load.
The usage of the database has changed and we aren’t using as much of the log as we used to.
We are billed at 2 am based on space used. We will grow the log back again after the billing period.
I need to clean up a large number of VLFs. (of course, then you are going to grow it back manually right?)
I quoted the caveats but Kenneth makes a solid case against shrinking log files without a good counterbalancing reason.