on pithru karyams

Neither dharmasastras or any decent norms of living would
prescribe that one should not look after his parents when they are alive.. 

It is
inappropriate to combine two non-connected issues namely caring for elders while they are alive and performing the last rites when they depart..

 The duties to be performed
in the service of parents during their lifetime are also enumerated in our
dharmasastras and such dictates  are part of any decent legislation and social norm  wherever civilized human beings exist.
But giving a decent burial and respect to the deceased is another issue of equally prime importance..

One thing has to be mentioned here .. We incur sins for both neglecting
parents when they are alive or after they are dead.. 

The belief is that Pithrus
do not have the same spirit of forgiveness as the living parents. A living
mother may forgive me even if I kick her... 

So, if we are to believe in the
traditions non-performance of rites to the departed souls can be more
dangerous..
I have no disagreement on the point that one should look after his near and dear
and especially the parents, very well, even making sacrifices at personal
levels.. and this has to be done even without the reinforcement of Sastras.. 

I
do not think our fathers and mothers nurtured and nourished us and also loved
us because it is prescribed  in the sastras..

 And, to look after the comforts of my mother,
I need not be reminded by any sastra.

 But the ceremonies after death are more
of social relevance and vary according to social and cultural norms.

 I mentioned
the Indian tradition here .
link  http://kanfusion.blogspot.in/2012/06/perfromance-of-rites-to-departed-kin.html
I do agree a son cannot be called grateful just because he performed the last
rites if he has not cared enough for the parents during their lifetime.. 

But
if, and only if, we believe in the traditions and sastras, non-performance of
rites after death is an act of ungratefulness and this inference is clearly
emerging from the basic social norms.. 

We are supposed to be born into this
world with pithru rina (debt to living and departed elders), deva rina etc and
it is our duty to pay back such debts through the prescribed rituals and
rightful life ..
 

A quote from Kalidasa's Abhijnana Sakunthalam, which is not exactly religious
text may be relevant here..
It underlines the importance of propitiating the pithrus and maintenance of the
race
अस्मात् परं बत यता
श्रुतिसम्भृतानि
को नः कुले निवपनानि
करिष्यतीति
नूनं प्रसूति विकलेन मया
प्रसिक्तं
धौताश्रुशेषमुदकं पितरः
पिबन्ति॥
asmāt paraṁ bata yatā śrutisambhṛtāni
ko naḥ kule nivapanāni kariṣyatīti
nūnaṁ prasūti vikalena mayā prasiktaṁ
dhautāśruśeṣamudakaṁ pitaraḥ pibanti||
it is in the sixth Act.. Dushyanta has neglected Shakuntala due to a
misunderstanding..and He has realized his folly and is depressed. He is also
aware that Shakuntala was pregnant when he abandoned her and he had lost the
only possible progeny and he had no other children.. He is also worried about
the lack of progenies after him to perform the last rites of his departed
elders.. He is exclaiming
"My pithrus are now drinking waters offered by me to them only to the extent of
what would remain after washing off their tears because they are always sad and
are shedding tears worrying that after this Dushyanta who is childless, there
is no one in their clan to perform and offer to them, as ordained in Shrutis,
the means of their survival in the pithru loka.."
So it was always a social responsibility to cherish one's own elders departed or
living..