I doubt there is anything sinister involved. In your case how could there be?
On the surface it does appear rather invasive especially if no detailed reasons were tabled.
It may well be as simple as seeing your paper cash-worthiness/disposable income with a view to pension advice, further cash injections and lump sum investments or they could be doing some sort of general share-holder driven exercise in controlling "bad book" potentials....of which you are clearly not a threat but a potential bar graph stat to add to "good book"
Financial institutions are very market-aggressive these days. We at home are constantly inundated with "suggestions" of what they think we should be doing with our retirement lumps despite being told we are happy with our arrangements. They don't smile at me or SWMBO when we go in, they are smiling at SWMBO's wee bits of retirement & inheritance accounts like slavering wolves sniffing her wallets, plying her with credit card facilities with eye-watering 4 figure limits that she simply does not require. Would you believe she was grilled two years back over coffee as to her intentions to flog her recently deceased mother's house? Being of a quiet and very private disposition, she found it uncomfortable and an invasion of privacy so we know how you feel.
I do agree with others a few straight questions directly to them seeking non-fudged direct answers are in order.
I would cut through the counter staff and go directly to one of their Business Managers..."why me in particular or is this some some sort of general fact finding mission"?
Frankly, just as in a domestic mortgage, if you are servicing the loan as agreed or even exceeding expectations, in my opinion now you have their money on trust and you are systematically keeping your end of the bargain true, it's got damn all to do with them how cash rich or "comfortable" you are. It's a bit odd for sure.
In true ARRSE fashion, personally I'd tell them to politely go forth and multiply.