How do we turn it around?
The more often we trim drafts correctly, the more likely they will develop sound bare hooves.  This eliminates the high cost of shoes, allows a budget for frequent trims and will reverse the cycle of huge, flared, flat, abscessing hooves.
Trimming draft hooves should be done as often as trimming the hooves of average horses.  Keeping them on a roughly 6 week schedule or less is best.  Yes, we can often get away with several months between trims, (better than no hoofcare ever) but the length of time that increases between trims decreases the horse’s ability to develop truly sound hooves. 

As horses evolved to varying degrees of size and weight, their hooves changed as well.  But is there a difference in structure or molecular density of hoof parts in hooves of varied dimensions?  Not according to my hoof nippers.
There are factors that cause hooves to differ from horse to horse: genetics, use and environment being a few, but draft hooves have the additional burden of supporting the largest, heaviest horses.
Same hoof – different weight bearing.
If nature intended the equine hoof to support the weight of an average or cob sized horse, what happens when that same hoof structure is supporting horses of varied weight and conformation?  Typically, the unattended hooves of our smallest equines grow disproportionate, upright/vertical wall and bars.  Why? The same hoof anatomy is supporting a petite body.
The opposite is true for derelict draft hooves which suffer with flared walls, quarter splits, flattened soles, and crushed bars.  Why?  The same hoof anatomy is supporting an epic body.
How Often Should Draft Horse Hooves Be Trimmed?
The struggle for sound hooves.
Drafts, more commonly than other equine types, are generally kept shod for many months at a stretch, whether that’s due to higher fees, and/or the difficulty in finding farriers willing to work on them, the negative effects are the same.  Shoes, consequently, can be the obstacles that keep drafts from being trimmed on a timely schedule. 
Equines, especially drafts, are frequent victims of a misguided notion that horses not being ridden have no need of hoof care – until something goes wrong.
Draft horses seen at public events are often supported by enormous and grotesque hooves.  Those hooves may appear impressive and fitting to the horse’s sheer size, but are not healthy or fully functioning, and often not pain-free, therefore shod.
Infrequent hoof trimming often leads to a host of hoof ailments including whiteline abscesses - a universally misdiagnosed condition that can require a long term rehab.  Then, sadly, owners unable to commit to extended hoof recuperation face the end of life decision for their heavy horses.

Draft horse hoof care is hard work!
Trimming the hooves of a flighty pony is annoying.  The flighty draft is dangerous.  A stubborn pony refusing to pick up a hoof is coaxed into cooperating.  When the draft refuses, it’s like trying to lift a tree trunk out of the ground.
With drafts, “nay means nay.”
For our more stubborn titanic equines, there are clever ways to overcome their obstinate refusals of hoof work.  Along with patience and imagination, try allowing them to eat hay while trimming and a sedative gel like dormosedan can disarm even the scariest giants.
Get started!
When we begin trimming a draft whose hooves are ravaged by neglect or dire trimming methods, we should start with rehabilitative trims every 4 weeks, if possible, to promote the growth of new wall angle and healthier connective structures.  After accomplishing that goal, draft hooves that are recurrently and correctly maintained will better serve our heavy equines.