Another angle to the straps/grip argument:
There's quite a compelling argument to support that when the grip fails it is actually an indicator of form breakdown elsewhere. Typically a follow-on effect from the upper back failing.
I know this sounds ass-backwards but hear me out. When looking at a lifters technique and deciphering where they are 'weak', the body can be quite hard to interpret. Sometimes what looks like one bodypart failing is in fact just the signal that form breakdown is occurring across the body.
The grip is a good example of this: Your grip begins to fail and the body's first response is to go into a bear hug...the shouders pitch forward, the upper back rounds, and the buck stops at the low back. The upper back failing can cause the grip to fail and the grip slipping can cause the upper back to round also.
The following is from a discussion I had on the topic some 9 years ago:
"Losing grip will tend to cause upper back rounding as the lifter attempts to regain grip. Upper back rounding itself can cause a weakened grip. i.e., both upper back rounding and grip weakening are potentially capable of causing the other.
If this is true, then losing grip is a sign that either form is breaking down, or form is about to break down. Losing grip can then be a signal to terminate the set for safety."
To tie this back in with what Steve has experienced. He may well have been a candidate for a 'relatively' weak upper back. Strengthening his upper back via the use of overload by the straps, allowing him to lift weights he might not have done without straps has improved his deadlift, without him suffering any ill-effects from the straps taking up the slack.