Just my guess: A realised loss in the options can be important or even critical, especially if always keeping 100% fully invested in either stocks or options, for analysis sack. Why not simply buying stocks or keeping just cash after crash? After crash, buying the same quantity of extremely expensive options, using any cash left after deducting realised loss, will easily generate a big loss potentially, when later the market price recovers and IV also recovers, i.e. at much lower value. Because the second round of buying more DITM could also possibly become OTM in a later date, losing a lot of IV values. That after crash might be good timing for selling ATM options! Instead of buying ATM! Just 2 cents again!
One potential benefit of using DITM calls: it helps non-US citizens that are subject to 30% withholding on dividends to pay less when the stock/ETF is a big yielder If the stock yields 6%, buying it outright will only deliver 4.2% in yield (due 30% tax). But if you buy DITM calls, the financing rate implied in the calls is probably less than 1.8% (maybe 1 to 1.5% most of the time?), so there are some savings (the interest rate would be a form of 'tax'). In this scenario the trader is not really using it for the leverage but for the tax savings, he does have the cash to buy 100% of the position but because he prefers to use the calls (due tax savings), he can invest the extra cash (the he didnt need to put down to finance the position) in UST bonds and earn extra interest. Assuming a 1% yield on the extra cash, he is paying barely anything to run the DITM call trade (something like 0.5% or less) The bigger the yield, the bigger the savings
The biggest advantage over margin is actually the embeded long put of a call vs the underlying on margin.