According to LinkedIn, an endorsement is a “one-click way for your connections to endorse the Skills & Endorsements listed on your profile.” A recommendation is a written statement of recommendation from a connection.” You can do both for other people and have other people do likewise for you. Why do you want endorsements and recommendations on your LinkedIn profile?
Your LinkedIn profile is not static, or shouldn't be anyway. It should be a cumulative representation of who you are and where you have been. If you aren't updating your profile, including comments from other people, you might as well pack it up and go home. While you can ask people to either recommend or endorse you for your skills or performance, it is always nice when your work and work ethic encourages people to take the initiative to comment without you asking them.
Job changes usually garner the most updates on LinkedIn profiles, but that is the barest minimum that many people change. They post no updates, do not take part in any discussion threads, and do not join any new groups after their initial page launch.
For people to be so lax on this incredible self-promotion opportunity makes me question how dynamic they would be as a colleague or client. Are they willing to try something new or are they stuck in the past? Are they flexible or intractable? These are the things I wonder about when I am looking for new opportunities. Do I want someone to drive the bus, or just wait on the curb for the next one to arrive? I don’t want the audience, I want the participants.