The lack of proper saved games is by far my biggest beef with modern PC games. It means the game is either trivially easy, or wastes your time in replaying sections repeatedly. The games that keep overwriting a single checkpoint file are the absolute worst, as mentioned earlier. I actually go out of my way to play the handful of games that let you save today. It's amazing that a feature that was once completely standard in PC gaming is now considered a great thing to have.
^ This + 1,000,000
Why Quick/Manual saves are a GOOD thing and why modern games have dumbed it down:-
1. Gamesave corruption has occurred to me and many others before. If you only have one autosave in one slot, then you are screwed and may have to abandon the game / restart from scratch. This isn't "fun", it's tedious and literally game-breaking. With the option of manual saves, you can easily alternate slots guaranteeing one "good" save no worse than 30-60mins old. Imagine an 80hr epic like Skyrim having only one autosave that gets corrupted after 70hrs of character development...
2. Bad Checkpoint placement. Checkpoint based saves can and do get screwy when auto-saving just before an incident which causes you to get stuck in a "death loop" (eg, 1 second before an attack against an NPC follower you must keep alive or in Metro where you forgot to purchase filters yet have to go outside, etc). Again, this isn't "fun", it's tedious. And it does nothing but punish gamers for taking time to explore an area instead of "rushing the railroad path".
3. Freedom of Branching. Occasionally it's fun to do something completely out of character. Eg, playing as a good guy but wanting to see what the consequences of a particular amusing / evil action is without it affecting your main game. Or maybe you just want to save a location to show someone else a certain scene later on. With multiple save slots, you can do this by branching one save off. "Checkpoint only" saves however (especially "one slot" only), do nothing but punish freedom of character development exploration.
4. Short gaming session length discrimination. When I was 13 I could pull 14hr gaming sessions easily. Now I'm 36 and have a full-time job and family, I'm lucky to get 1hr per day - and that 1hr may not be one continuous hour, it may be broken up into 3x sessions of say 24mins, then 13mins then 23mins parts. I do not want to have to replay the same 25mins apart "checkpoint" area over and over again just because the developer couldn't be bothered to implement a simple quick save system that's at least 1% more advanced than 1980's cartridge based console systems. Yet again - forced replayment (after successful completion of area) due to falling 5 meters / seconds short of some arbitrary checkpoint placement is not fun it's tedious. I have reached the point in the past in 2 or 3 "checkpoint only" games, where I've literally uninstalled an unfinished game simply from being sick of treated like an idiot for not guessing the "right length" of gaming session in advance or being punished for not having a lifestyle like an unemployed 12 year old who can devote a whole weekend of morning to midnight for one game.
5. There are plenty of cross-platform games which manage to have BOTH auto-saving checkpoints AND an optional quicksave for those who want it and do so flawlessly, so there's no real excuse for big budget games to not have them. Bioshock 1&2, Deus Ex, Dragon Age, Mass Effect, Oblivion, Skyrim, and dozens more all managed it, so why is it so hard for a 2014 game to achieve what was basically standard from 1993-2010 games (including what 1993 original Doom managed in 4MB RAM under MS-DOS 5.0 before DirectX 1.0 was even invented)?...
Checkpoint only systems aren't being "clever" or "shaping a challenge" by removing "quicksave spamming" (bad gamers who resort to that will simply continue to use other cheats / trainers), it's just 100% dumbing down & unnecessary consolization compromise for everyone else's freedom of choice.