Your thinking is flawed and shows a lack of understanding about the two companies and their core business model. Apple predominantly make designer lifestyle products, Microsoft are predominantly a software company. It's not just all about profit, it's about market share of product and the worlds business industry runs on Microsoft software as well as most of the home market, if you did a little research into both companies your view might change? If Apple start making enterprise business software that made inroads into the business sector, then maybe Microsoft would be under serious threat? But Apple don't and aren't likely too either.
If people stopped buying the iPhone (very unlikely, but a more possible scenario) their profits would plummet as fast as they grew and all they would have to fall back on would be iTunes and a very small computer hardware/software product line. The iTunes business model is not based on rock solid foundations either, many musicians don't like it, as it does virtually nothing to support or nurture current talent or introduce new talent like an A&R department, it's purely an income generator for Apple, but at the moment they are forced to accept it. OS X isn't and never has been a market leader, Windows O/S and it's derivatives is and is likely to remain so for some considerable time. There is a place for both companies, they overlap but their core business models differ.
Have a look at Netmarketshare, their stats are current up to March 2015
Try Allway Sync or Microsoft SyncToyI just want a simple piece if software to replicate what I do manually, dump unaltered files on to a second removable drive
As for the OP - to rely purely on a NAS as a backup system is asking for trouble, Network Attached Storage is not a foolproof backup system and neither is RAID. A SAN (Storage Area Network) might be considered more of a backup system as it has more effective disaster recovery, but even then data is normally backed up to tape for archiving should the SAN itself suffer a catastrophic failure. I have to agree with the 'simple' approaches suggested by Gazjam and Juha or get the best of both world's a simple NAS for convenience and multiple user access, but you will need to have that data backed up and a collection of HDD with duplicated data. I have three complete data sets. My working data set, a local backup and an off-site backup, which is swapped with the local one every few weeks. These are just bare HDD as I can swap them out of my workstation without the need for any USB connections. I also retire hard drives regularly, rather than wait for them to fail.
I use Allway Sync for backups and Acronis True Image for disk imaging as I also keep full disk image backups, should my workstation drives suffer a failure. I just swap them over and I have a working computer again in minutes.