And not like newer versions do not introduce new bugs? I've spent thousands of hours playing on 1.6.4 and have not encountered some pretty serious bugs which are present in newer versions, such as one that is often reported that corrupts chunks for no reason (not due to a game crash or improper shutdown):
Minecraft 1.8.1, Minecraft 1.8.8, Minecraft 15w44b, Minecraft 1.8.9, Minecraft 15w51b, Minecraft 1.9 Pre-Release 3, Minecraft 1.9 Pre-Release 4, Minecraft 1.9, Minecraft 1.9.2, Minecraft 1.9.4, Minecraft 16w21b, Minecraft 1.10.2, Minecraft 16w40a, Minecraft 1.11, Minecraft 1.11.2, Minecraft 1.12 Pre-Release 7, Minecraft 1.12.1
I see quite a few people posting crash reports for newer versions as well, yet I've never had any crashes that were not due to mods or doing something silly like setting off a Superflat TNT world, or possible in current versions (e.g. stack overflow error due to water/gravel in certain situations, mainly due to 32 bit Java using a smaller stack by default, fixed with a simple JVM argument to use the 64 bit stack size).
Of course, I've fixed some bugs myself - including ones which are still not fixed as of 1.12.2; for instance, ever noticed how lighting is weird in staircases, among other areas (despite the versions listed this has been around for far longer than just 1.7.4)?
MC-43968 Ambient occlusion bug (With partial fix)
Affects Version/s: Minecraft 1.7.4, Minecraft 1.8.1-pre3, Minecraft 1.8.2, Minecraft 1.8.4, Minecraft 15w42a, Minecraft 1.10.2, Minecraft 16w41a, Minecraft 16w42a, Minecraft 16w43a, Minecraft 1.11, Minecraft 1.11.2, Minecraft 17w14a, Minecraft 1.12, Minecraft 1.12.1 Pre-Release 1, Minecraft 1.12.1
Note that they actually show what needs to be done to mostly fix this bug yet Mojang just says "not important!", as they do with numerous other bugs; for example:
MC-42053 Low mob spawn rates on low render distances
MC-2536 View distance affects mob spawning
Affects Version/s: Minecraft 1.4.2, Minecraft 1.4.6, Minecraft 1.5.1, Minecraft 1.5.2, Minecraft 1.6.2, Minecraft 1.6.4, Minecraft 13w38a, Minecraft 13w38b, Minecraft 13w38c, Minecraft 1.7.1, Minecraft 1.7.2, Minecraft 1.7.4, Minecraft 1.7.5, Minecraft 14w11b, Minecraft 1.7.9, Minecraft 14w33c, Minecraft 1.8, Minecraft 1.8.1-pre3, Minecraft 1.8.1-pre5, Minecraft 1.8.1, Minecraft 1.8.3, Minecraft 1.8.7, Minecraft 1.8.9, Minecraft 1.9, Minecraft 1.10.2, Minecraft 16w40a, Minecraft 17w06a, Minecraft 1.12
(this bug only started affecting singleplayer in 1.7.4 (the first bug report) due to chunk loading being made dependent on render distance - why not do what Optifine does in 1.6.4 and limit the minimum chunk load distance to 10 but allow it to go higher as needed? Or, you know, actually fix the bug by making mob despawn distance (viewdistance - 2) * 16 blocks, with a maximum of 128 and a minimum view distance of perhaps 5 so mobs are active within a reasonable range on 2-4 chunk render distance; the current minimum used by the server is 3, which only allows entities to be ticked within a 3x3 chunk area around the chunk the player is in)
The first issue may also have to do with the fact that the client does not wait for the internal server to shut down (a longer shutdown time due to deoptimized code could be why it is far more common since 1.8) - which has an extremely simple fix (just make the client wait for the server to fully shut down before letting you do anything else), which also fixes numerous other bugs, such as worlds not deleting properly or worlds simply disappearing from the saves menu (again, without a crash or improper shutdown; if you quit the game normally while the server is still saving it is the same as forcibly closing it).
And, of course, the more features that are added the more bugs pop up.