Nope I had to unlock them, but if you want to make it so you have to unlock them too. Go to the console and type in sv_unlocked_chapters 0 (maybe it's 1).
Then your X-Box or Game Disc is haunted. Either by a mysterious saved game beyond your knowledge (family member had the game and completed it without your knowledge) or a string of poorly advised coding that unlocks the game for all first-timers. Very Strange
just recently, i opened CSS and it made me do an update, though i looked on the steam news and there was no update, then after that i opened HL2, and only the first 4 chapters were unlocked, though i have beaten HL2 countless times, im well over 20 times now, so who knows wha thappenes, seems it was quite the opposite to u, but what happened to u did happen to me in HL:source.