From my experience 95+% of deer hits, with vehicles, happen at night.
Do you often drive at night ?
I spent 30+ years driving BC mountain roads at night to get from town to first my cabin and then my home; I only hit one deer, in all that time.
JMHO: Deer whistles , yes , Roo-Bar , overkill ; and if you do your own servicing you'll grow to hate it.