There isn't a hint of a budget constraint.

Increasing the income will shift the budget constraint right since more of both can be bought, and decreasing income will shift it left.

Given the fundamental nature of the budget constraint, these differences between needs mirror systematic changes in the expenditure shares of consumption as income rises.

This guarantees the constancy of the budget constraint and vastly simplifies the problem of how the consumer should adjust consumption over the life-time.

In this respect, the flypaper effect occurs because citizens are unaware of the true budget constraint.