Why are the lakers not signing free agents to counter what the Celtics are doing?

I think the lakers should add someone for the playoff run and to show there fans that they are in it to win it. Also to counter what the Celtics are doing!!! I think they should try to get Steve Francis, PJ Brown, Robert Horry, Antoine Walker, Sam Cell, or Jason Williams. Some of those guys are old but are former Celtics and it would stick it to the Celtics to bring in a former Celtic.