The header issue above is the most common one, but it's not the only place an install in this area gets complicated. Track spacing on 1990-era openings sometimes runs narrower than what current standard doors ship with, which means either a custom-width order or modified jamb brackets - neither of which a big-box installer quoting a flat price over the phone accounts for.
The other place it goes sideways is scheduling. This crew works out of Glendale, about 14 miles from Sun City West, so an install here gets planned as a full appointment, not a same-day add-on between other jobs closer to the shop. If your header needs reinforcement discovered on site, that's a second piece of material and sometimes a second trip - we'll tell you on the spot if that's the case rather than force a door onto a header that isn't ready for it.