Why do certain Valve games/mods take sooo long to load up on the title screen?

[-$ilver-]

It will just be the blurred out background and takes about a minute and thirty seconds to be able to do anything- like view the menu and start a new game, load a previous game, change options, etc. Most Valve games or mods do this that I have. It's not a real problem. I expect it by now.
It's charming in a way. But I am just curious why "they" do it all the time. Other games both older, same year(s) and newer, do not take so long. Just Valve games it feels like or are most noticeable anyway. Thank you.

[DUKE NUKEM]

Step 1. Update to SSD.
Step 2. Join the rest of us in the 21st century.

[cSg|mc-Hotsauce]

I haven't noticed this since the days of 1.6 to HL2.

[Satoru]

More than likely your anti virus is locking the files causing the delays. White list the directory

[-$ilver-]

Początkowo opublikowane przez Satoru:

More than likely your anti virus is locking the files causing the delays. White list the directory

For only Valve games?

[-$ilver-]

Początkowo opublikowane przez DUKE NUKEM:

Step 1. Update to SSD.
Step 2. Join the rest of us in the 21st century.

That did not answer the question, why does only Valve's games do this. Other games on Steam do not.

[G. S.]

Greatness makes you wait...