There are at least two reasons. First one is malfunctioning strut itself (leakage). Second one is holders which attache struts to the car body have some rubber parts inside. As time goes the rubber parts wear off and fail.
In the first case you have to replace the fail strut(s). For the second one you have replace the holders.
Sometimes it happens you that you have to replace struts as well as holders.
Struts.
The 1999 Toyota Camry has struts on the front and rear of the car.
I have a 92 Toyota Camry (same model as yours) and they have struts on all four.
Toyota Camry requires 4 struts - 2 front and 2 rear.
A rattle in the right front fender of a Toyota Camry may indicate that you need a wheel alignment. It could also point to a problem with your struts.
Yes, Camry 99 has struts on the front as well as on the back.
All Toyota Camry's have struts in the front. This is also accompanied with strut mounts and bearings that are located between the mount & strut. I highly recommend replacing the mounts & strut bearings with the struts. My experience has shown that the mounts fail before the strut.
Struts in the front, shocks in the rear.
The 2007 Toyota Camry has 57.8 in. of front shoulder room.
The 2013 Toyota Camry has 54.5 in. of front hip room.
The 2009 Toyota Camry has 57.8 in. of front shoulder room.
The 2006 Toyota Camry has 41.6 in. of front leg room.