Usually the reason why c7-c5 isn't played immediately is because it invites complications if white tries to blast open the center right away. Against slower moves black doesn't need to be in a hurry to play c7-c5. Although against some of these moves I think that 2...c5 is an underestimated option.
1. d4 d5 2. Nf3 c5 3. c4! is awkward to deal with as black. The best is probably to transpose into the Tarrasch with 3...e6 which certainly makes the variation playable but it's not everyone's cup of tea.
The variation 2. Nc3 c5 I believe is good for black, even though it's a chigorin with an extra tempo it's not easy for white to make use of this tempo. 2...Nf6 is simply more natural as it stops white from playing e2-e4 and doesn't invite immediate complications.
After 1. d4 d5 2. Bg5 c5 I have some vague memory that white wants to take on c5 and follow up with e4.
2...c5 is to my knowledge good against both 2. Bf4 and 2. e3 but black is in no hurry to play this move.
I don't think 1. d4 d5 2. e4 c5 requires any comment.
Pretty good answer, Smnrkssn. Your first paragraph about "complications" make it sound as if Black wants to play an opening without doing much thought. If that's the case, it seems like the solution is for Black to counter "complications" is to memorize more lines of his defense.
I partly agree with your second paragraph about the Tarrasch, but again I believe it just requires Black learning more lines of that defense.
I agree about the Blackmar Gambit, too. I included that just to be more complete, and for comparision purposes. That must be one of the "complications" to which you are referring. With that risky pawn sacrifice going on, ...c5 does seem overshadowed by that more important matter.
Anyway, thanks for your opinion, which sheds some light on this topic that I've been wondering about for the past month.
In the following recent thread...
https://www.chess.com/forum/view/chess-openings/1d4-d5-2nf3-instead-of-c4?page=2
...somebody mentioned that if White neglects to play a Queen's Gambit by playing a nonforcing move instead, then Black should immediately seize the opportunity to do so. That has been my general opinion, too, since the most popular White response to 1. d4 d5 is 2. c4, which suggests the Queen's Gambit is the most powerful d4 opening. However, for some reason most Black players do not jump at that opportunity when it arises, per database statistics.
Why don't Black players jump at this opportunity more often?
Below are some database results that show this lack of interest by Black to play a reversed Queen's Gambit. Note that often ...c5 is often way down at #5 to #8 in popularity, despite Black often having good statistical results with it.
1. d4 d5 {Queen's Pawn Game. w 40%.}
2. c4 {Queen's Gambit. #1 pop. w 41%.}
2. Nf3 {"Pogorelov Attack." #2 pop. w 39%.}
2...Nf6 {#1 pop. "Beliavsky Defense." w 38%.}
2...c6 {#2 pop. n 36%.}
2...e6 {#3 pop. w 41%.}
2...Nc6 {#4 pop. w 49%.}
2...c5 {#5 pop. n 34%.}
2. Nc3 {Chigorin Variation. #3 pop. w 38%.}
2...Nf6 {"Karayev Defense," q.v. #1 pop. w 38%.}
2...e6 {#2 pop. w 42%.}
2...Bf5 {#3 pop. b 37%.}
2...c6 {#4 pop. w 36%.}
2...Nc6 {#5 pop. b 49%.}
2...f5 {#6 pop. w 45%.}
2...g6 {#7 pop. w 40%.}
2...c5 {#8 pop. b 43%.}
2. Bg5 {Levitsky Attack. #4 pop. w 43%.}
2...h6 {pt.}{#1 pop. n 37%.}
2...c6 {#2 pop. w 36%.}
2...Nf6 {#3 pop. w 48%.}
2...Nd7 {#4 pop. w 52%.}
2...f6 {#5 pop. b 39%.}
2...Bf5 {#6 pop. w 49%.}
2...c5 {#7 pop. w 47%.}
2. e3 {"Quintas Attack." #5 pop. b 38%.}
2...Nf6 {#1 pop. b 41%.}
2...e6 {#2 pop. w 46%.}
2...Bf5 {#3 pop. wb 37%.}
2...Nc6 {#4 pop. w 52%.}
2...c6 {#5 pop. b 40%.}
2...c5 {#6 pop. b 46%.}
2. Bf5 {Mason Variation. #6 pop. w 40%.}
2...Nf6 {"Krush Defense." #1 pop. w 39%.}
2...e6 {#2 pop. w 41%.}
2...c5 {#3 pop. nb 34%.}
2. e4 {Blackmar Gambit. #7 pop. w 45%.}
2...dxe4 {"Locher Defense." #1 pop. w 42%.}
2...e6 {#2 pop. w 50%.}
2...c6 {#3 pop. w 40%.}
2...Nf6 {#4 pop. w 55%.}
2...Nc6 {#5 pop. b 48%.}
2...c5 {#6 pop. w 70%.}