In most real time games seeding the random number generator is pretty much unnecessary as although the same numbers will be generated in the same sequence it is highly unlikely that the user's experience is going to be exactly the same each time due to the fact that their own decisions / actions will unlikely be identical from game to game.
For example - a user fires a stream of bullets which generates some particle effects that may include some calls to 'rand()' or 'rnd()'. If in game 1 the player fires a stream for 1 second and in game 2 the player fires a stream for 1.5 seconds then the number of calls of the 'rand' function will differ between the two games at the same point in time meaning that from that point on no two events relying on the random number generator will be at the same point in the sequence. The further and further along the game gets the more divergent the two games will become with respect to the random number sequence as the position in the random number sequence will differ at every event thereafter.
Furthermore - even in a totally deterministic game that does not rely on calling the random number generator, unless it is turn based, it is highly improbable that the exact same experience will be provided to the player anyway.
The main case where it becomes an issue is for procedural generation of the environment in which case 'seedrnd millisecs()' becomes useful.
For example - a user fires a stream of bullets which generates some particle effects that may include some calls to 'rand()' or 'rnd()'. If in game 1 the player fires a stream for 1 second and in game 2 the player fires a stream for 1.5 seconds then the number of calls of the 'rand' function will differ between the two games at the same point in time meaning that from that point on no two events relying on the random number generator will be at the same point in the sequence. The further and further along the game gets the more divergent the two games will become with respect to the random number sequence as the position in the random number sequence will differ at every event thereafter.
Furthermore - even in a totally deterministic game that does not rely on calling the random number generator, unless it is turn based, it is highly improbable that the exact same experience will be provided to the player anyway.
The main case where it becomes an issue is for procedural generation of the environment in which case 'seedrnd millisecs()' becomes useful.