For me, the problem is that it requires internet access. When I found that WhatsApp was deleting important messages and that the backups and exports that I was counting on were useless, as I mentioned in another comment[1], I found that the easiest way to save those messages was to scrape them from the web client. However, connecting the phone to the internet meant that it would receive more messages and hence delete more messages. I took screenshots manually of several days of the oldest available messages to avoid losing them, but it wouldn't have been necessary if the desktop client didn't require internet access.
[1] https://news.ycombinator.com/item?id=19669740