The Bible uses the term 'Shalom'. Most people think it just means peace, but it is far more encompassing than that. A better term might be 'wellbeing', but also 'restoring the Status Quo'. When you look at the OT laws through that lens there is a clear tendency towards restoration - including restoration of freedom in this case - nobody should feel short-changed or resentful, because that leads to escalation (and we have seen that in the race riots of a year ago, riots that didn't solve anything because they just continued the resentment).
In conclusion: Don't assume that a law dealing with the death of a servant/slave somehow means it was normal behaviour. Clearly it isn't (if the slave could love his master or the fact that he was answerable for the death). Whatever we think about slavery now doesn't change what they thought then. The laws in general indicate that it was not a good thing for Israelites to go into slavery, but rather that it was a necessity to ensure survival. There are probably plenty of people in the third world who would indenture themselves for 7 years if they were guaranteed food and shelter for themselves and their families.