Route not following trails on map went sent to Oregon 300

Can anyone tell me if I'm doing something wrong, or if this is just a limitation of the Oregon 300? It's an older unit I've had for years but never really used, and wanted to use for a hike next week. When I make a route in basecamp it follows the hiking trail with just a few points, but when I send to to the Oregon 300, it's just straight lines. Anyone have any advice?

Here is a Oregon 300 Screenshot  and a BaseCamp screenshot showing the difference.