Yes, I have an HDMI to VGA adaptor in my backpack, but it doesn't fit in my pockets. See the photos to get an idea about the size limit. It also needs external power, so I'd need to carry a barrel jack to USB wire too.

I wish I could fit a Lightning to HDMI adaptor, but it's physically huge compared to the other adaptors, and I wonder whether Apple's likely to change to USB-C on future iPhones and iPads. Therefore I feel like WiFi is a more universal data source. Latency is slow, but that's not a problem for PPT slides.