Radeng,
Don't disagree but look at other service industries that used to offer customer facing staff.
The customer, as you rightly say, pay the wages of all involved in aviation. However, the customer buys (or not) a product that is offered at a price. It is the product that is changing.
Sadly, I think that within 5-7 years, airport check-in as we know and love/hate it at present will be a thing of the past. 99.9+% of passengers will self check in one way or another and some carriers will not offer 'personal' assistance at airports; others will. Such is competition and product variance.