I believe that the lack of detachable leads is a cost saving measure.

I personally prefer a welder with detachable leads...having them makes
it much easier and cheaper to attach a HF TIG unit to the welder. Or if
it is a AC only unit, to connect a homemade DC bridge to the welder to
get DC capability.

A few years ago, I bought a returned Sears (made by Century) AC/DC arc
welder that was returned to the store.

It too had detachable leads. When I priced what the different male
plugs/female sockets were worth to do a TIG conversion on a welder that
doesn't have them, I soon learned that you don't want to buy a welder
without them.

I also have a Miller 180SD TIG welder. When I opened the machine up to
check out the construction, I was surprised as to the construction of
the main rotary switch. The blades of this switch do not have a
definite detent and if one is not careful, arcing can easily occur if
the switch is not wriggled to seat the blades. After using a Lincoln
buzz box that had a switch that seated itself with a loud clunk, it is
at least one detail I think Miller could improve on.

I too have noticed alot of Lincolns and very few Millers. I do believe
it is because Lincoln targeted that market niche. The Lincoln is built
like a tank and will stand abuse with no maintainance to speak of. I
have seen many Lincolns with their fans stopped by mouse nests and the
welder will continue to shrug off the lack of cooling without a
complaint.

FYI...the going price for a Lincoln (with mask and some rod) seems to
be around $50 in private sales and $100-125 at auctions.

TMT