Front tyre wear

Aquila

I have a 2007 Hyundai Santa Fe, 2.2 auto diesel.

I noticed on returning from 4 months away that the inside of the front tyres were scrubbed clean of tread. I have done 30,000 miles since thay were replaced, about 6,000 of which was towing a 1,500 kg caravan. I had the alignment checked and it was OK. I
do load the car up when we are travelling. so what's caused the tyre wear? The tyre man thought the car might be light on the front causing less pressure on the suspension. Is this credible? Do I need to load less in the car or make sure it's more midships.

Any suggestions would be welcome. The previous tyres, before I started towing, lasted 60,00 miles, all Hankook.