A general contractor usually fulfills the following functions:
(2) materials lists, purchasing and delivery,
(3) coordination with architects or designers,
(4) scheduling the project and keeping it on schedule,
(5) working out the cost of the project and keeping the project on budget,
(6) identifying and hiring subcontractors, installers and workers,
(7) obtaining permits and inspections,
(8) managing the project,
(9) ensuring project and workmanship quality,
(10) ensuring safety in the work site,
(11) paying subcontractors and workers,
(12) coordinating insurance, bonds, payments, etc.,
(13) coordinating communication between homeowner and work crew,
(14) managing change orders.
In brief, general contractors manage the remodel on behalf of the homeowner. If you are confident performing these tasks, you might not need a contractor. If you are not, you need to hire a good general contractor.