Diameter of column after the reflux condenser?

[tiramisu]

Seeking knowledge from my betterers....

This is something I have been wondering about for quite a while.
Not being any kind of enginerd or HVAC magician I mostly just copy what I see and am happy with what works...

I have noticed that most of the reflux stills columns that I have seen reduce the column diameter after the reflux condenser.

Does this result in result in improved(?)/increased velocity flow to the product condenser and is this for some reason a gooder thing?

OR

Is this simply a cost savings where a 2" product condenser has no problem keeping up with a 3 or 4" reflux condenser
so don't bother wasting your money on bigger pipes?

Thanks in advance,
t