Reward relationship between doctors and pharmaceutical companies?

It's a Known fact that pharmaceutical companies often incentivise doctors to prescribe their specific brand of medicines. However, not all doctors choose to accept these incentives; some do, while others do not. For those who do accept these incentives, what are their preferences usually? Pharmaceutical companies typically reward them with various gifts, such as perfumes and watches, and some companies provide cash directly.

In case of money….. - To the best of my knowledge, doctors generally prefer receiving cash. They do not receive this money in their bank accounts, and pharmaceutical companies also avoid transferring funds through banks. Why?

In case of gifts….. - Most of the items doctors receive are easily affordable for them. Given the choice between gifts and money, what do they usually prefer, and why?