A NEETcel is either (1) someone who believes that their status as a NEET is a major contributor to their inceldom, or (2) someone who is an incel and also is a NEET, either because they see no point to working (since they cannot betabuxx), or for other reasons. Many incels are discriminated against in the workplace for their looks or poor social skills, so it becomes a contributing factor in why they become NEETs.
Some incels are NEET for political reasons as they do not wish to contribute taxes to a purse which disproportionately benefits normies, Chads and Stacy's r just sex-havers in general. These incelists argue that a large proportion of single mothers who produced children from their wild hooking-up during their teens and 20s eventually become single mothers on welfare. As such, since incels were not invited to these hooking up parties, incelis wonder why they should pay for the after-effect of a party they were excluded from. To incels, this makes about as much sense as paying the rent of a random person you do not know, halfway across the world. Others have chosen the NEETcel path out of misanthropy, and subsequent unwillingness to engage in a society they feel has rejected them.