Home inspections have traditionally been for the benefit of the purchaser.  "Listing Inspections" benefit all parties - purchasers, vendors and Realtors.

Deals Won't Fall Through
Home inspections, performed as a condition of the offer, can kill deals. Sometimes this is because the purchaser gets cold feet; sometimes there's a big problem no one knew about. Sometimes it is because the house has been mis-represented; sometimes it is because the home inspector scared the purchasers by not explaining that minor and typical problems are just that - minor and typical.

If the home inspection is performed prior to the house being listed, all parties will be aware of the physical condition of the house before an offer is drawn. There will be no surprises after the fact. Deals will not fall through.

Repairs Prior To Sale
Sometimes, the home inspection will reveal items which should be repaired immediately. A  "Listing Inspection" allows the vendor to repair the problem prior to putting the house on the market.

If the inspection occurs after the Agreement of Purchase and Sale, the purchaser could walk, renegotiate or, depending on the inspection clause, the vendor may have the option to repair. A repair done by an unmotivated vendor may not be the best repair and may not meet the purchasers' expectations. This has caused to many deals in my experience to not close.

Peace Of Mind For The Purchaser
There is no doubt that part of the value of a home inspection is a guided tour of the house for the prospective purchaser. We can return to do a walk-through with the purchaser, if requested at one half of the original inspection fees.

Avoid Renegotiation
In a buyers' market, most houses have to be sold twice. It takes a lot of work to get a signed Agreement of Purchase and Sale. Then the home is inspected and the purchaser wants to renegotiate.

If all parties know the condition of the house prior to the offer, there is no need for renegotiation. Actually if they if they understand all of the defects up front and choose to make an offer, then they really can't back out for the results of the home inspection.

A vendor who pays for a home inspection will be further ahead than one who has to renegotiate. He of she may even sell the house faster.

Unrealistic Vendors
An inspection at the time of listing can also help a Realtor deal with a vendor who has unrealistic expectations. The inspection report is good ammunition for explaining why you can't ask top dollar for a house that is not in top condition.

Reputable Inspection Companies
 A "Listing Inspection" will only have value if the home inspection company is perceived to be reputable, qualified and properly insured. Prospective purchasers will have little or no faith in a report done by someone they perceive to be in the vendors', or Realtors' pocket.

Summary
These are only my opinion and I believe that the future of home inspection lies in "Listing Inspections". Offers are cleaner and deals are less likely to be renegotiated or fall through.  A "Listing Inspection" affords purchasers, vendors and Realtors the information to protect everyone's interest.