Because you LUFFS us Dreaming!
And we feel so much better when you're having a shit time of it because we can all go, 'Well, at least I haven't got twins/three/two with reflux.' 
It sounds par for the course bordering on good for this thread Sunbeam. But one very good point that Elizabeth Pantley makes in No Cry Sleep Solution is that there is no 'bad' infant sleep. There is a wide spectrum of 'normal' infant sleep (which yours most definitely is) and there are the parents' responses and feelings towards it. If the latter is negative, that's where the feeling of Something Must Be Done comes in. So if you and your DP don't like the way things are, then your DS's sleep is as bad as its effect on you, IYSWIM. How did it go with Sian today?
Eden DS2 was 4 August
When you've had one tough, non-sleeping baby, a second one is not NEARLY so bad because you have every coping strategy down to a fine art and you're (mostly) hardened to the sleep deprivation. You also don't sweat it, moider, stew, tear your hair and hate your never-endingly sleepless life because you know it will end, you know you're not going to die, and you accept that, actually, every nap with a baby in your lap parked in front of Netflix is a pretty sweet deal. It's when you do it the wrong way round like Dreaming (easy one first) that it bites you on the arse. 
And YY to wanting to be violent towards those who falsely tell you that sleep improves on a steady trajectory. What a fecking con.
I found a website with a table which, among other things, tells you roughly how long they should be awake between naps at what age - very handy and something I definitely stick to to avoid demon overtired baby. I have it bookmarked, but am thinking of getting rid of it for my own sanity because of the 'other things' on it - how long the longest stretch of night sleep should be (yep, lengthens each month to that magical, mythical stretch of 12 hours, which DS1 has never done and that DS2 doesn't even come close to), how many night feeds they should be on (DS2 'should' be on 0-1 night feeds, apparently. I don't think he got the memo
), how many hours of daytime sleep they 'should' be having and how many naps...the writer insists she breastfed exclusively and has worked with 'hundreds of families' who all managed this continuous improvement with her marvellous methods. I call bullshit.