Some more comprehensive insurance policies will offer routine care cover as standard, but others won't even give you the option to add it.
This might be because their policies already cover much of what is included in routine care, or it might be because they don't think they can provide a policy that's of value to you, for a price that is appealing.
Remember to check if a certain provider has routine care included as standard; it could explain why the monthly premium is slightly higher.