I am sure that manufacturers adopted detachable power cords for a practical reason...so that they could easily configure their products for sale in different countries that use different configurations of electrical outlets. This opened an oportunity for the "upgrade" business that has been thoroughly exploited.
If you think that the wire which the manufacterer used is somehow inadequate, a few feet of new wire should cost only a few dollars. The new wire should be soldered in place just like the original "captive" wire. A soldered connection is always better than any plug. (Besides, the captive approach discourages "PC rolling" that could bankrupt you!) While you have the chassis open you might like to count up how many "push on" connections there are between the power cord and the transformer. The power switch, the fuse holder and the transformer itself are frequent offenders, but some designs have many more. You might consider hitting these spots with the solder while you are in there.
If you think that the wire which the manufacterer used is somehow inadequate, a few feet of new wire should cost only a few dollars. The new wire should be soldered in place just like the original "captive" wire. A soldered connection is always better than any plug. (Besides, the captive approach discourages "PC rolling" that could bankrupt you!) While you have the chassis open you might like to count up how many "push on" connections there are between the power cord and the transformer. The power switch, the fuse holder and the transformer itself are frequent offenders, but some designs have many more. You might consider hitting these spots with the solder while you are in there.