Why exactly ? The previous poster is right i would say. Will has no job, no reasonable plans to get one - he is searching only because Penny (implicitly) ordered him to. He has some idea about writing poetry, but there are two problems - a) it is difficult to make a living doing anything like that, b) If he will not work, deal with problems of common people, whatever he will write will be unappealing to most of us, since he will be far from the important issues - art should serve a social function, trying to improve society.
As it was pointed out already, Penny is probably searching for somebody much more reliable and stable. It is still possible that Will will (

) improve under her influence, and become a 'proper man' but otherwise, she will most likely get too fed up with his ineptness.
(Also this means that except for some very weird accident , she will be unlikely to get pregnant (therefore in QC-verse it just might happen))
Also , saying these things is not merely reflecting an idea within our society - not being able to take care of yourself is a biological putoff, just like being a cripple (not saying that people with disabilities are necessarily unworthy in this respect, just pointing out that that particular trait is obviously one of the negatives about any such afflicted person) since such person is unlikely to ensure a good future for the common offspring Imagine a caveman who sucked at hunting and lived from others' scraps instead - would any cavewoman be interested in getting involved with him?
If Will lived somehow on his own, this would be less problematic even if the source of his living was social security, but currently he seems to leech his family, and is likely to be a similar burden on Penny if they lived together.