If there are old, large trees check if they are healthy. Removing large, dying tree is expensive.

Not much sense in bringing in an electrician for a house that was built a couple of years ago, however if the house is 80 years old and the wiring hasn't been updated recently, then an electrician may be a good idea.

Based on what a good one sees you then might want to have an area expert (structural, electrical, plumbing, roofer) further review serious problems that have been identified.

Even in states that try to regulate, the profession is very hot or miss.

First and foremost, all HGTV shows are staged and therefore must be taken with a grain of salt.
Second, a "Holmes" inspection is not a true home inspection, as he has the luxury of being told of the problems the buyers are having post purchase, and the luxury of dismantling systems, opening walls, etc that is not possible when a home inspector is inspecting a home that his/her client does not yet own.
What seller is going to allow an invasive "Holmes" inspection of their home?

It is true that there are the good, the bad and the in between in terms of quality with home inspectors...as is the case with all professions.

IMO, buyers greatly increase their chance of getting a poor inspection if

1) They hire an inspector based upon the cheapest fee
2) If they wait until the last minute to hire and just go with the real estate agents recommendation without performing any due diligence
3) If they fall for the hype of an onsite or same day report (which benefits the inspector but screws over the buyer), ditto for a "written" report that is mostly boiler plate.
4) Fail to take some time to familiarize themselves with what is and is not included in a home inspection, either in accordance with state licensing and absent that, nationally accepted standards.
5) Fail to ask to see a sample report before they hire.
6) Fail to ask to review the pre-inspection agreement before they hire.

A home is THE biggest investment most people make...but time and again, all too many go for the bargain basement inspector using the "eeny, meany, miney mo" form of choosing who gets the job.

Excellent HI's do exist...buyers just need to be willing to do their homework..and THEN choose.

At least one of plumbers I had work on projects in the past few years did not know how to make or repair a poured lead and oakum cast iron pipe joint.

He knew how to cut out the suspect joint and use no-hub CI (uses rubber boots and clamps to joint the sections) but no idea how to repair the joint (clean it out- re-pack, re-pour lead and tighten).

It has been out of favor for a long time and he is in his late 20s.
Houses generally only are required to meet the building code in effect when they where built, and in effect when additions or major changes are made.

Wiring and plumbing may be VERY 'out of date' by modern standards, but still perfectly functional and acceptable, even if they are not convenient..

Grandfathering of existing work goes back almost forever (there are a few exceptions in some places fr limited things).

GFCI kitchen and bathroom protection and smoke detectors are two common 'required' upgrades at sale.

Without grandfathering, we would be tearing houses apart every time a new code revision came out.