Because there's still a benefit to a synchronous interaction. The bot can perform first level troubleshooting, ask for clarification, begin to form a plan and get your buy-in, etc. When you just have a fire-and-forget email form, you're going to have incomplete reports, missing information, people who have no idea what they're talking about, and who knows what else.

I bet 95% of calls to a plumber are the same ten or so issues— leaky faucet, toilet won't flush or is clogged, laundry machine overflowed, omg there's water everywhere, etc. If the bot is able to suss out the situation and also get a sense what kind of solution the customer is looking for and on what timeframe (cleanup now because I'm having a party tomorrow, install a $3000 sump pump in two weeks, etc) that can skip over a lot of exhausting email back and forth and get to something much more like what GP experienced, where they had one brief, synchronous interaction, followed by a single followup with the proposed actions that was exactly what he knew he wanted.