Because if you were an important hire you'd be impressed more when the comp was eventually pushed all the way to 250 from 200 than to 250 from 230. There is no advantage in offering you 225 or 230 at all.
If I was an important hire I probably have a handful of 230s in my hand already. It’s easy for me to not bother with a company who may or may not push from 200 to 250.
If you had a handful of 230s you would not negotiate? That's quite rare, most companies optimize hiring for the most probable case, not for the outliers.
Because you could use your offers against each other as a leverage, dropping any of the offers decreases your leverage. Most people want more leverage when negotiating, not less.
