Armhole shaping help

I am new to making sweaters. I am wondering why you decrease x number of stitches at the beginning of the next 2 rows and not at the beginning and ending of the same row, which makes more sense to me. Anybody?

I’ve only done seamless sweaters so I’m not sure. If you have a link to the pattern it might help.

Welcome to Knitting Help!

If a pattern says to BO at the beg of the next 2 rows it’s for the underarms, and you can’t BO at the end of a row. A regular dec can be done on both the beg and end of a row, but only one or two sts; a BO is usually 3 or more sts.

It makes the curve. I am doing a purse with that same thing and it makes a curve that goes up to a strap.

Unless it is a sleeve perhaps a raglan(?) then how many sleeves curve from both sides? I just finished doing fronts on my son’s hoody and I don’t think the neckline should curve like an armhole.