https://wikimediafoundation.org/wiki/Maps_Terms_of_Use requires a valid HTTP User-Agent or Referer which identifies the source of maps requests.
There are some legitimate use cases for Refererless browsers, but these are low traffic like loading a single tile in a browser and shouldn't hit any rate limits.
Implementing delay pools for User-Agents claiming to be browsers but not sending a Referer is how the OSMF implemented this: https://github.com/openstreetmap/chef/pull/79
It's better to implement this before its needed, even if the rate limits are high, because when its needed, it's needed urgently. There should also be fewer issues with setting false expectations if we have it set up this way from the start.