What is the need for nirvana?

If, according to Buddhist doctrine, it is not the ego-consciousness but merely karmic continuity that transmigrates across rebirths, then on what grounds should one be motivated to seek liberation from saṃsāra? Since there is no enduring self that experiences the cumulative burden or existential drudgery of suffering across lives, and since the sufferings of past or future existences are not personally felt by the present individual, what compelling basis remains for the soteriological urgency central to Buddhist thought?