Can we use HPLC to purify an organic reaction product?
For semiprep applications, you need larger columns, because you cannot just increase the concentration (at least not a lot) with a normal one. You can get along with an analytical column using an automated system running over the weekend, but that too fails if you want to scale up by another order of magnitude.

A HPLC pump that can run at 100x the standard flow rate is likely twenty times as expensive. The column will be much more expensive. The larger volume needs totally different safety considerations. And so on ...

As Waylander commented, you can do preparative HPLC at a pinch and save your day (or your dissertation), but to use it as a standard lab procedure is most often un..sustainable. ;)