What if you left your phone at home and it's not connected to the Internet?.

I usually leave my phone at random places in my house and have to find it and 'wake it up' so that it connects to the wifi and I can use Whatsapp web.

no gif upload support

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