yeah you're missing something, unless you're just running something low priority like a personal blog:
Although an app may not require the resources of more than a single dyno, we recommend running at least 2 dynos for a production app. One reason for this is that dynos restart roughly every 24 hours, and dyno redundancy helps ensure that you don't experience excessive queueing or dropped requests while a single dyno restarts. Additionally, dynos and the processes running on them can occasionally crash, and having another dyno helps ensure that you don't have downtime while that dyno recovers. Finally, single web dynos sleep after an hour of inactivity, and having a second dyno means that all dynos will stay awake.[1]
Although an app may not require the resources of more than a single dyno, we recommend running at least 2 dynos for a production app. One reason for this is that dynos restart roughly every 24 hours, and dyno redundancy helps ensure that you don't experience excessive queueing or dropped requests while a single dyno restarts. Additionally, dynos and the processes running on them can occasionally crash, and having another dyno helps ensure that you don't have downtime while that dyno recovers. Finally, single web dynos sleep after an hour of inactivity, and having a second dyno means that all dynos will stay awake.[1]
[1] https://blog.heroku.com/archives/2013/4/26/introducing_produ...