Here's why atv's now come with keys:

3-wheelers only had the emergency kill switch, any one could start them, and take them.

The manufactures decided to put keyed switches on to reduce theft of quads, a good selling point, and some theft deturrent.

In the same forum you see people who have quads stolen you also see tips on how to hot wire quads.

It is easy enough for some low life to take your quad without the key by pushing it, or stealing many quads buy stealing your trailer after you tied all your quads down for them. We shouldn't give tips for any one who comes in here how to hotwire a quad, that might not have been smart enough to figure it out.

 

I lost a key to my Honda XL600 and gave the ignition to a key shop and they made a key from it.