In general, law enforcement agencies have resisted reforms even when those reforms have been proven to be effective in saving lives, providing better service or improving inefficiencies. Resisted might be too strong of a word. We have been slow to adopt changes even though these changes are for the better.
As an example, only recently has most agencies adopted a mandatory seat belt policy for officers. Even today, some departments do not require their officers to wear a seat belt even though it has been proven that wearing a seat belt saves lives; even though most departments work to educate the public about this life saving device; even though all states have a mandatory seat belt law.
Similarly, body armor is a lifesaver for police officers, yet many departments do not provide this equipment for their officers or have a mandatory wear policy. A recent survey suggested that over 90% of police departments now require officers to wear body armor compared to 59% in 2009, which is a big improvement.